Number of subsets of {1,2,3,...,n} that sum to 0 mod 6.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =6a(6) =12a(7) =22a(8) =44a(9) =88a(10) =172a(11) =344a(12) =688a(13) =1368a(14) =2736a(15) =5472a(16) =10928a(17) =21856a(18) =43712a(19) =87392a(20) =174784a(21) =349568a(22) =699072a(23) =1398144a(24) =2796288a(25) =5592448a(26) =11184896a(27) =22369792a(28) =44739328a(29) =89478656