a(n) = n*(11*n-5)/2.

Terms

a(0) =0a(1) =3a(2) =17a(3) =42a(4) =78a(5) =125a(6) =183a(7) =252a(8) =332a(9) =423a(10) =525a(11) =638a(12) =762a(13) =897a(14) =1043a(15) =1200a(16) =1368a(17) =1547a(18) =1737a(19) =1938a(20) =2150a(21) =2373a(22) =2607a(23) =2852a(24) =3108a(25) =3375a(26) =3653a(27) =3942a(28) =4242a(29) =4553