a(n) = 4*n^3 - 6*n^2 + 6*n - 2 + (-1)^n.

Terms

a(0) =1a(1) =19a(2) =69a(3) =183a(4) =377a(5) =683a(6) =1117a(7) =1711a(8) =2481a(9) =3459a(10) =4661a(11) =6119a(12) =7849a(13) =9883a(14) =12237a(15) =14943a(16) =18017a(17) =21491a(18) =25381a(19) =29719a(20) =34521a(21) =39819a(22) =45629a(23) =51983a(24) =58897a(25) =66403a(26) =74517a(27) =83271a(28) =92681a(29) =102779