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

Terms

a(0) =20a(1) =175a(2) =840a(3) =2940a(4) =8400a(5) =20790a(6) =46200a(7) =94380a(8) =180180a(9) =325325a(10) =560560a(11) =928200a(12) =1485120a(13) =2306220a(14) =3488400a(15) =5155080a(16) =7461300a(17) =10599435a(18) =14805560a(19) =20366500a(20) =27627600a(21) =37001250a(22) =48976200a(23) =64127700a(24) =83128500a(25) =106760745a(26) =135928800a(27) =171673040a(28) =215184640a(29) =267821400