Number of subsets of {1,2,3,...,n} that sum to 0 mod 20.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =2a(7) =6a(8) =14a(9) =26a(10) =52a(11) =103a(12) =205a(13) =410a(14) =820a(15) =1640a(16) =3278a(17) =6554a(18) =13108a(19) =26216a(20) =52432a(21) =104860a(22) =209716a(23) =419432a(24) =838864a(25) =1677728a(26) =3355448a(27) =6710888a(28) =13421776a(29) =26843552