A Pell convolution.

Terms

a(0) =1a(1) =0a(2) =4a(3) =4a(4) =17a(5) =32a(6) =88a(7) =200a(8) =497a(9) =1184a(10) =2876a(11) =6924a(12) =16737a(13) =40384a(14) =97520a(15) =235408a(16) =568353a(17) =1372096a(18) =3312564a(19) =7997204a(20) =19306993a(21) =46611168a(22) =112529352a(23) =271669848a(24) =655869073a(25) =1583407968a(26) =3822685036a(27) =9228778012a(28) =22280241089a(29) =53789260160