a(n) = C(n+6, 6) - n - 1.

Terms

a(0) =0a(1) =5a(2) =25a(3) =80a(4) =205a(5) =456a(6) =917a(7) =1708a(8) =2994a(9) =4995a(10) =7997a(11) =12364a(12) =18551a(13) =27118a(14) =38745a(15) =54248a(16) =74596a(17) =100929a(18) =134577a(19) =177080a(20) =230209a(21) =295988a(22) =376717a(23) =474996a(24) =593750a(25) =736255a(26) =906165a(27) =1107540a(28) =1344875a(29) =1623130