a(n) = (n+1)*(n+2)^2*(n+3)*(n+4)*(n+5)*(2*n+3)/720.

Terms

a(0) =1a(1) =15a(2) =98a(3) =420a(4) =1386a(5) =3822a(6) =9240a(7) =20196a(8) =40755a(9) =77077a(10) =138138a(11) =236600a(12) =389844a(13) =621180a(14) =961248a(15) =1449624a(16) =2136645a(17) =3085467a(18) =4374370a(19) =6099324a(20) =8376830a(21) =11347050a(22) =15177240a(23) =20065500a(24) =26244855a(25) =33987681a(26) =43610490a(27) =55479088a(28) =70014120a(29) =87697016