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 A382845 #11 Apr 13 2025 16:11:56
%S A382845 -1,1,1,7,17,49,127,337,881,2311,6049,15841,41471,108577,284257,
%T A382845 744199,1948337,5100817,13354111,34961521,91530449,239629831,
%U A382845 627359041,1642447297,4299982847,11257501249,29472520897,77160061447,202007663441,528862928881,1384581123199
%N A382845 Sum of the legs of the unique primitive Pythagorean triple (a,b,c) such that (a-b+c)/2 = A000045(n) and its long leg and hypotenuse are consecutive natural numbers.
%D A382845 Miguel Ángel Pérez García-Ortega, José Manuel Sánchez Muñoz and José Miguel Blanco Casado, El Libro de las Ternas Pitagóricas, Preprint 2025.
%H A382845 Miguel-Ángel Pérez García-Ortega, <a href="/A382845/a382845.pdf">El Libro de las Ternas Pitagóricas</a>
%F A382845 a(n) = A382843(n,1) + A382843(n,2).
%F A382845 a(n) = 2*Fibonacci(n)^2 - 1.
%e A382845 For n=4, the short leg is A382843(2,1) = 3 and the long leg is A382843(2,2) = 4 so the sum of the legs is then a(4) = 3 + 4 = 7.
%t A382845 a=Table[Fibonacci[n],{n,0,30}];Apply[Join,Map[{2#^2-1}&,a]]
%Y A382845 Cf. A000045, A382843, A382844, A095122, A007598, A080097.
%K A382845 sign,easy
%O A382845 0,4
%A A382845 _Miguel-Ángel Pérez García-Ortega_, Apr 06 2025