a(n) = n*(7*n+3)/2.

Terms

a(0) =0a(1) =5a(2) =17a(3) =36a(4) =62a(5) =95a(6) =135a(7) =182a(8) =236a(9) =297a(10) =365a(11) =440a(12) =522a(13) =611a(14) =707a(15) =810a(16) =920a(17) =1037a(18) =1161a(19) =1292a(20) =1430a(21) =1575a(22) =1727a(23) =1886a(24) =2052a(25) =2225a(26) =2405a(27) =2592a(28) =2786a(29) =2987