a(n) = 12spt(n) + (24n - 1)p(n), with a(0) = -1.

Terms

a(0) =-1a(1) =35a(2) =130a(3) =273a(4) =595a(5) =1001a(6) =1885a(7) =2925a(8) =4886a(9) =7410a(10) =11466a(11) =16660a(12) =24955a(13) =35191a(14) =50505a(15) =70252a(16) =98085a(17) =133455a(18) =182819a(19) =244790a(20) =329121a(21) =435420a(22) =576030a(23) =752609a(24) =984165a(25) =1271998a(26) =1643460a(27) =2105450a(28) =2693522a(29) =3420235