This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A329178 #21 Nov 09 2019 10:52:16 %S A329178 1,3,5,11,19,34,62,107,191,335,587,1035,1812,3184,5589,9803,17213, %T A329178 30199,52999,93014,163214,286439,502655,882095,1547991,2716503, %U A329178 4767160,8365776,14680889,25763219,45211237,79340227,139232411,244335770,428779502,752455475 %N A329178 Sum of the products of pairs of Padovan numbers which are two apart, starting from A000931(5). %F A329178 a(n) = Sum_{i=5..n+5} A000931(i)*A000931(i+2). %F A329178 a(n) = A329227(n+7) - 1. %F A329178 Conjectures from _Colin Barker_, Nov 09 2019: (Start) %F A329178 G.f.: (1 + x - x^2 + x^3 - x^4) / ((1 - x)*(1 - 2*x + x^2 - x^3)*(1 + x - x^3)). %F A329178 a(n) = 2*a(n-1) - 2*a(n-4) + 2*a(n-5) - 2*a(n-6) + a(n-7) for n>6. %F A329178 (End) %e A329178 For n=3, a(3) = 1*1 + 1*2 + 1*2 + 2*3 = 11. %o A329178 (Python) %o A329178 p = lambda x:[1, 1, 1][x] if x<3 else p(x-2)+p(x-3) %o A329178 a = lambda x:sum(p(i)*p(i+2) for i in range(x+1)) %Y A329178 Cf. A000931, A133037, A329227. %K A329178 nonn %O A329178 0,2 %A A329178 _David Nacin_, Nov 08 2019