a(n) = (2*n - 1)*(7*n^2 - 7*n + 6)/6.

Terms

a(0) =1a(1) =10a(2) =40a(3) =105a(4) =219a(5) =396a(6) =650a(7) =995a(8) =1445a(9) =2014a(10) =2716a(11) =3565a(12) =4575a(13) =5760a(14) =7134a(15) =8711a(16) =10505a(17) =12530a(18) =14800a(19) =17329a(20) =20131a(21) =23220a(22) =26610a(23) =30315a(24) =34349a(25) =38726a(26) =43460a(27) =48565a(28) =54055a(29) =59944