a(n) = binomial(n,13).

Terms

a(0) =1a(1) =14a(2) =105a(3) =560a(4) =2380a(5) =8568a(6) =27132a(7) =77520a(8) =203490a(9) =497420a(10) =1144066a(11) =2496144a(12) =5200300a(13) =10400600a(14) =20058300a(15) =37442160a(16) =67863915a(17) =119759850a(18) =206253075a(19) =347373600a(20) =573166440a(21) =927983760a(22) =1476337800a(23) =2310789600a(24) =3562467300a(25) =5414950296a(26) =8122425444a(27) =12033222880