2*p^2, for p an odd prime.

Terms

a(0) =18a(1) =50a(2) =98a(3) =242a(4) =338a(5) =578a(6) =722a(7) =1058a(8) =1682a(9) =1922a(10) =2738a(11) =3362a(12) =3698a(13) =4418a(14) =5618a(15) =6962a(16) =7442a(17) =8978a(18) =10082a(19) =10658a(20) =12482a(21) =13778a(22) =15842a(23) =18818a(24) =20402a(25) =21218a(26) =22898a(27) =23762a(28) =25538a(29) =32258