a(n) = floor(C(n+8,8)/C(n+2,2)).

Terms

a(0) =1a(1) =3a(2) =7a(3) =16a(4) =33a(5) =61a(6) =107a(7) =178a(8) =286a(9) =442a(10) =663a(11) =969a(12) =1384a(13) =1938a(14) =2664a(15) =3605a(16) =4807a(17) =6325a(18) =8222a(19) =10571a(20) =13455a(21) =16965a(22) =21206a(23) =26295a(24) =32364a(25) =39556a(26) =48032a(27) =57970a(28) =69564a(29) =83028