(1/6) times the sum of the elements of all subsets of [n] whose sum is divisible by six.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =2a(5) =7a(6) =20a(7) =49a(8) =132a(9) =330a(10) =786a(11) =1892a(12) =4472a(13) =10368a(14) =23940a(15) =54720a(16) =123836a(17) =278664a(18) =622896a(19) =1383672a(20) =3058720a(21) =6729184a(22) =14738688a(23) =32157312a(24) =69907200a(25) =151461952a(26) =327158208a(27) =704648448a(28) =1513680192a(29) =3243601280