a(n) = (9*n^2 + 3*n + 2)/2.

Terms

a(0) =1a(1) =7a(2) =22a(3) =46a(4) =79a(5) =121a(6) =172a(7) =232a(8) =301a(9) =379a(10) =466a(11) =562a(12) =667a(13) =781a(14) =904a(15) =1036a(16) =1177a(17) =1327a(18) =1486a(19) =1654a(20) =1831a(21) =2017a(22) =2212a(23) =2416a(24) =2629a(25) =2851a(26) =3082a(27) =3322a(28) =3571a(29) =3829