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

Terms

a(0) =1a(1) =8a(2) =35a(3) =111a(4) =287a(5) =644a(6) =1302a(7) =2430a(8) =4257a(9) =7084a(10) =11297a(11) =17381a(12) =25935a(13) =37688a(14) =53516a(15) =74460a(16) =101745a(17) =136800a(18) =181279a(19) =237083a(20) =306383a(21) =391644a(22) =495650a(23) =621530a(24) =772785a(25) =953316a(26) =1167453a(27) =1419985a(28) =1716191a(29) =2061872