a(n) = 9*J(n)^2 where J(n) are the Jacobsthal numbers A001045 with J(0) = 1.

A323210

a(n) = 9*J(n)^2 where J(n) are the Jacobsthal numbers A001045 with J(0) = 1.

Terms

    a(0) =1a(1) =9a(2) =9a(3) =81a(4) =225a(5) =1089a(6) =3969a(7) =16641a(8) =65025a(9) =263169a(10) =1046529a(11) =4198401a(12) =16769025a(13) =67125249a(14) =268402689a(15) =1073807361a(16) =4294836225a(17) =17180131329a(18) =68718952449a(19) =274878955521

External references