There is in Washington one group that, more than any other, sees little to look forward to on weekends - low-income city blacks.

Those with annual incomes of less than $10,000 - a group accounting for possibly one-third of all blacks in the District of Columbia - seem to participate less in the activities that make weekends pleasant for most people, including others of similarly low income.

Of the 93 per cent who reported their incomes in a Washington Post survey, 17 per cent fell into the less-than-$10,000 category. The count was 61 blacks and 94 others the "others" being blacks outside the city and low-income whites.

Survey reseatchers generally feel that a random sample of 61 people it too small for statistically valid complex analysis, is large enough for gross determinations and the uncovering of patterns.

Perhaps the most nagging finding in the survey was that differences in activities between the low-income city blacks and other are not solely a matter of money. The contrasts come between low income blacks and low-income whites as well.

For example, among the population at large, 35 per cent say their favorite summer weedend activity is going to the beach or enganging in water sports. When the figure is broken down by income, 24 per cent of the low-income people as a whole rank it as favorite activity. Among inner-city low-income blacks, that fiugre drops sharply to 8 per cent, while for all other blacks it is 22 per cent.

It is as if low-income city blacks have come to terms with an economic reality that doesn't hold for others: They feel that they can't go to the beach and they simply don't think about it.

And while they truned on TV sets in the same proportions as other people, low-income city blacks watched considerably longer. They were also less likely to engage in active sports - or to visit with friends.

Overall, the pattern was consistent: They have less wherewithal and their activities and more constricted.

In the affluent Washington area, more than half the families onw their won homes, but only one in eight of the lower-income city black families wons or is buying its home, according to the Post poll.

While the poll shows some 18 per cent of all marriages in the area ending in divorce or separation, the rate for low-income city blacks appears to be about twice that.

And a great many of these blacks either have no jobs at all or must work weekends at what is essentially cleanup work.

When people in general were asked whether they enjoy eddkends more than weekdays, 53 per cent said yes, while 40 per cent saw little difference.

Among low-income city blacks, those figures were reversed. Small wonder.