Number of subsets of {1..n} whose mean is an integer, where {} has mean 0.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =9a(5) =16a(6) =27a(7) =46a(8) =77a(9) =136a(10) =239a(11) =426a(12) =769a(13) =1400a(14) =2571a(15) =4762a(16) =8857a(17) =16568a(18) =31139a(19) =58734a(20) =111165a(21) =211044a(22) =401695a(23) =766418a(24) =1465489a(25) =2807672a(26) =5388783a(27) =10359850a(28) =19946833a(29) =38459624