(1/n) times the sum of the elements of all subsets of [n] whose sum is divisible by n.

Terms

a(0) =1a(1) =1a(2) =4a(3) =4a(4) =12a(5) =20a(6) =40a(7) =70a(8) =150a(9) =284a(10) =564a(11) =1116a(12) =2212a(13) =4392a(14) =8768a(15) =17404a(16) =34704a(17) =69214a(18) =137980a(19) =275264a(20) =549340a(21) =1096244a(22) =2188344a(23) =4369196a(24) =8724196a(25) =17422500a(26) =34797476a(27) =69505628a(28) =138845940a(29) =277383904