a(n) = binomial(n+6,6)*(6*n+7)/7.

Terms

a(0) =1a(1) =13a(2) =76a(3) =300a(4) =930a(5) =2442a(6) =5676a(7) =12012a(8) =23595a(9) =43615a(10) =76648a(11) =129064a(12) =209508a(13) =329460a(14) =503880a(15) =751944a(16) =1097877a(17) =1571889a(18) =2211220a(19) =3061300a(20) =4177030a(21) =5624190a(22) =7480980a(23) =9839700a(24) =12808575a(25) =16513731a(26) =21101328a(27) =26739856a(28) =33622600a(29) =41970280