a(n) = 3*(n+1)*binomial(n+5,6).

Terms

a(0) =6a(1) =63a(2) =336a(3) =1260a(4) =3780a(5) =9702a(6) =22176a(7) =46332a(8) =90090a(9) =165165a(10) =288288a(11) =482664a(12) =779688a(13) =1220940a(14) =1860480a(15) =2767464a(16) =4029102a(17) =5753979a(18) =8075760a(19) =11157300a(20) =15195180a(21) =20424690a(22) =27125280a(23) =35626500a(24) =46314450a(25) =59638761a(26) =76120128