Four-oh-six is back. With the opening last night of five impressive exhibitions in that steep-staired, art-filled building -- at 406 Seventh St. NW -- the gallery-going season here feels under way in earnest. In the single downtown block of Seventh Street NW -- between the WPA, at 404, and Lansburgh's, at 420 -- there are a dozen shows to see.

Some of Washington's best artists are among those represented. Ellen MacDonald's large and layered canvases are at the WPA. Next door, at 406, Jane Haslem is exhibiting Joe Shannon, he of the self-portraits and the scary, myth-filled dreams; and John Van Alstine, the former Washingtonian, has a grand show at Osuna's; Barbara Kornblatt is displaying new paintings by Willem de Looper; McIntosh/Drysdale -- once again in town after three long years in Texas -- is marking its reopening with a big and big-name group show; and David Adamson is showing Washington's William Newman, an artist who has fallen for a machine. Willem de Looper

Willem de Looper, the Phillips Collection's curator, is, by birth, a Dutchman, and for many years his paintings, even those produced here, called to mind the peace, the cool mists and flat fields, of his calm and level homeland. But that is true no longer. His canvases, which once seemed studies in serenity, now are filled with movement, energy and bounce. His colors once suggested northern skies and northern seas. Now they seem to burn.

Though his paintings are untitled, and though they are abstractions, one diptych now at Kornblatt's ("Untitled No. 8") might be called "Mount St. Helens." A triangle of black looms against a midnight sky. Its apex has exploded. Freely dancing brush strokes of green and gold and orange leap into the air. Despite the charred black of the mountain and the force of the eruption, the work is free of menace. Those upward-swirling colors carry their own light. They feel like happy flames.

De Looper works in the tradition of the Washington Color Painters. Once his art suggested strictness. Though he never cared for masking tape or rulers, though one always felt his hand, his geometries were rigorous and his passions were contained. But that old somberness has now been overturned by fun.

Little violet dots chase after one another at the lower left of "Untitled No. 6"; terra cotta waves, or perhaps dragons' teeth, fill the band beside them. Waving blue and silver stripes, wobbling like friendly drunks, bump into one another in "Untitled No. 4." The field those stripes fill is framed in unexpected streaks of orange, red and gold. All of these new pictures, even those that feel most stern, seem to smile at the viewer. Little marks of red and mauve, like so many kisses, tickle the black rectangle of "Untitled No. 10."

His colors are well-tuned, but that is not surprising considering the years he has spent at the Phillips. These are the most accomplished -- and the most entertaining -- paintings he has done. His show closes Oct. 16. McIntosh/Drysdale Reopens

The best news at 406 is that Nancy Drysdale is back. The 30-artist group show arranged for her reopening here surveys her career -- and demonstrates convincingly why she has been so missed.

Many local galleries are relatively insular. Drysdale, in contrast, sells expensive objects by many of the nation's best-known advanced artists: Alice Aycock of the astonishing constructions, William Wegner (whose photographs made famous his late Labrador, Man Ray), Tom Wesselmann of the grand nudes, Valerie Jaudon, Ned Smyth, Leon Golub, Scott Burton and Robert Kushner are among those represented in this large, nostalgic show.

Also on display is a curious little picture by Jonathan Borofsky, "Upsidedown Vase of Flowers No. 1" (1976). Borofsky is a hit now. His full-fledged retrospective is traveling the country and will open in December at the Corcoran. But he was hardly known when Drysdale first showed him. "Upsidedown Vase of Flowers" is, in fact, the first picture she ever sold.

Her art career in Washington began 11 years ago when she became director of Max Protetch's gallery on P Street. She took over the next year and, in the fall of 1980, moved to 406. Two years later, when her husband took a temporary job in Houston, she moved her gallery to Texas. Now it occupies the third-floor space at 406 that once was Harry Lunn's.

Sculptor Martin Puryear (who once lived here), the late Gene Davis and Washington's Jerry Clapsaddle are among the artists she has shown before and is showing once again. The Clapsaddle on view is titled "She Came Back," which, indeed, she did. Her show closes Oct. 19. William Newman

"Have Faith in Magic" is the title of William Newman's mechanized and sexy show at David Adamson's. Newman, 37, who's been teaching at the Corcoran for a dozen years, draws with brushes, pencils, Q-tip swabs, even paper towels. Because he has a skillful hand, and can catch a likeness, one is surprised to find here that he of late has placed his faith not in magic only but in digitizers, pixels and a Macintosh computer.

The artist has a storeroom filled with photographs he's torn from books and magazines. But he no longer needs them. Now his borrowed images -- of Tom and Jerry, Elvis, Betty Boop and the Cheshire cat -- are hey-look-ma-no-hands pictures produced by his machines.

The young couple he's portrayed in "Whatcha' Thinkin'-Mitsubishi Electric" are lost in their own thoughts. So, soon enough, are we: His thoughts -- of Miss Boop and Miss Universe -- appear in a red panel by his cogitating image; hers -- of war and warriors -- float next to her head. The couple is hand-painted. But the pictures of their thoughts are computer-generated stills mechanically extracted from videotapes and television shows.

Newman says he likes to paint with "three TVs and the stereo on. The more happening, the better." And one sees that in his art. The blue nude thrashing in ecstasy in his "Having Faith" is portrayed on two strips of plastic, one black and one white. Her body has been drawn with colored pencils, but her hair is splattered paint, as if dripped by Jackson Pollock. Newman varies his materials. Other pictures here are done on paper or on cloth.

One of them, "Impress Me," blends romantic play and menace. The male figure in it appears to be strangling his love, until we notice she is laughing. Another unexpected laugh -- a giant, slow-dissolving one -- is suggested by the Cheshire cat that grins behind their heads. The cat's face was both drawn and distorted by computer. Only if one puts one's face flush against the wall, and views the painting from the side, can one read it clearly.

Newman's art has long explored the dreaminess and angers and shifting viewpoints of romance. That odd device, that stretching-out, makes clear what was before implied: Relationships are fluid, passing time distorts the sure, lovers rarely share a single point of view. "Have Faith in Magic" will run through Halloween.