n*Jacobsthal(n).

Terms

a(0) =0a(1) =1a(2) =2a(3) =9a(4) =20a(5) =55a(6) =126a(7) =301a(8) =680a(9) =1539a(10) =3410a(11) =7513a(12) =16380a(13) =35503a(14) =76454a(15) =163845a(16) =349520a(17) =742747a(18) =1572858a(19) =3320497a(20) =6990500a(21) =14680071a(22) =30758222a(23) =64312669a(24) =134217720a(25) =279620275a(26) =581610146a(27) =1207959561a(28) =2505397580a(29) =5189752159