a(n) = binomial(n+2,2) + binomial(n+3,3) + binomial(n+4,4) + binomial(n+5,5).

Terms

a(0) =4a(1) =18a(2) =52a(3) =121a(4) =246a(5) =455a(6) =784a(7) =1278a(8) =1992a(9) =2992a(10) =4356a(11) =6175a(12) =8554a(13) =11613a(14) =15488a(15) =20332a(16) =26316a(17) =33630a(18) =42484a(19) =53109a(20) =65758a(21) =80707a(22) =98256a(23) =118730a(24) =142480a(25) =169884a(26) =201348a(27) =237307a(28) =278226a(29) =324601