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

Terms

a(0) =5a(1) =20a(2) =55a(3) =125a(4) =251a(5) =461a(6) =791a(7) =1286a(8) =2001a(9) =3002a(10) =4367a(11) =6187a(12) =8567a(13) =11627a(14) =15503a(15) =20348a(16) =26333a(17) =33648a(18) =42503a(19) =53129a(20) =65779a(21) =80729a(22) =98279a(23) =118754a(24) =142505a(25) =169910a(26) =201375a(27) =237335a(28) =278255a(29) =324631