a(n) = binomial(n,16).

Terms

a(0) =1a(1) =17a(2) =153a(3) =969a(4) =4845a(5) =20349a(6) =74613a(7) =245157a(8) =735471a(9) =2042975a(10) =5311735a(11) =13037895a(12) =30421755a(13) =67863915a(14) =145422675a(15) =300540195a(16) =601080390a(17) =1166803110a(18) =2203961430a(19) =4059928950a(20) =7307872110a(21) =12875774670a(22) =22239974430a(23) =37711260990a(24) =62852101650a(25) =103077446706a(26) =166509721602