Sum of squares of pentanacci numbers (A001591).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =6a(7) =22a(8) =86a(9) =342a(10) =1303a(11) =5024a(12) =19424a(13) =75120a(14) =290416a(15) =1122160a(16) =4337009a(17) =16762634a(18) =64787534a(19) =250400910a(20) =967783566a(21) =3740437902a(22) =14456621263a(23) =55874162432a(24) =215950971648a(25) =834640190272