Sequence of sums of alternating powers of 3.

Terms

a(0) =1a(1) =4a(2) =5a(3) =14a(4) =17a(5) =44a(6) =53a(7) =134a(8) =161a(9) =404a(10) =485a(11) =1214a(12) =1457a(13) =3644a(14) =4373a(15) =10934a(16) =13121a(17) =32804a(18) =39365a(19) =98414a(20) =118097a(21) =295244a(22) =354293a(23) =885734a(24) =1062881a(25) =2657204a(26) =3188645a(27) =7971614a(28) =9565937a(29) =23914844