f = lambda x,y:[n for n in range(1<<x+y)if bin(n).count('1')==y]
for (x, y) in (0, 1), (1, 1), (3, 2):
print (x, y), f(x, y)
ZiA9IGxhbWJkYSB4LHk6W24gZm9yIG4gaW4gcmFuZ2UoMTw8eCt5KWlmIGJpbihuKS5jb3VudCgnMScpPT15XQoKZm9yICh4LCB5KSBpbiAoMCwgMSksICgxLCAxKSwgKDMsIDIpOgoJcHJpbnQgKHgsIHkpLCBmKHgsIHkp
(0, 1) [1]
(1, 1) [1, 2]
(3, 2) [3, 5, 6, 9, 10, 12, 17, 18, 20, 24]