a(n) = 7*(n+1)*binomial(n+6,7)/2.

Terms

a(0) =7a(1) =84a(2) =504a(3) =2100a(4) =6930a(5) =19404a(6) =48048a(7) =108108a(8) =225225a(9) =440440a(10) =816816a(11) =1447992a(12) =2469012a(13) =4069800a(14) =6511680a(15) =10147368a(16) =15444891a(17) =23015916a(18) =33649000a(19) =48348300a(20) =68378310a(21) =95315220a(22) =131105520a(23) =178132500a(24) =239291325a(25) =318073392a(26) =418660704a(27) =546031024a(28) =706074600a(29) =905723280