a(n) = binomial(n + 4, n - 1) + 1.

Terms

a(0) =1a(1) =2a(2) =7a(3) =22a(4) =57a(5) =127a(6) =253a(7) =463a(8) =793a(9) =1288a(10) =2003a(11) =3004a(12) =4369a(13) =6189a(14) =8569a(15) =11629a(16) =15505a(17) =20350a(18) =26335a(19) =33650a(20) =42505a(21) =53131a(22) =65781a(23) =80731a(24) =98281a(25) =118756a(26) =142507a(27) =169912a(28) =201377a(29) =237337