a(n) = T(4,n), array T given by A048505.

Terms

a(0) =1a(1) =26a(2) =87a(3) =233a(4) =577a(5) =1377a(6) =3217a(7) =7409a(8) =16881a(9) =38129a(10) =85489a(11) =190449a(12) =421873a(13) =929777a(14) =2039793a(15) =4456433a(16) =9699313a(17) =21037041a(18) =45481969a(19) =98041841a(20) =210763761a(21) =451936241a(22) =966787057a(23) =2063597553a(24) =4395630577a(25) =9344909297a(26) =19830669297a(27) =42010148849a(28) =88852135921a(29) =187636383729