(1/7) times the sum of the elements of all subsets of [n] whose sum is divisible by seven.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =2a(5) =5a(6) =15a(7) =40a(8) =97a(9) =237a(10) =571a(11) =1385a(12) =3263a(13) =7618a(14) =17580a(15) =40146a(16) =90962a(17) =204618a(18) =457446a(19) =1016494a(20) =2247000a(21) =4943400a(22) =10828248a(23) =23625120a(24) =51358776a(25) =111277576a(26) =240359368a(27) =517697136a(28) =1112090144a(29) =2383049792