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 A236381 #15 Apr 30 2025 16:23:50
%S A236381 1,1,4,2,64,59,1342,1076,4268,10739,64387,818998,3226976,26444853,
%T A236381 53155423,1175849126,13396689992,2368807981,907313696551,483703442648,
%U A236381 2835669288809,98713800566163,24423236756993,6054940274199961,17628259859562384,128658404383205917,3865377837569367511
%N A236381 Smallest value of x such that x^2 + y^2 = P, where P is the product of the first n primes of the form 4k + 1, and 0 < x < y.
%e A236381 a(3) = 4 because the solutions to x^2 + y^2 = 5*13*17 are (x,y) = (23,24), (9,32), (4,33), (12,31) of which the smallest value of x is 4.
%o A236381 (PARI) prd(n) = my(q=3, t=1); for(k=1, n, until(q%4==1, q=nextprime(q+1)); t*=q); t; \\ A006278
%o A236381 a(n) = {my(t=prd(n), q=0); until(issquare(t-q^2), q++); q; } \\ _Michel Marcus_, Mar 05 2021
%Y A236381 Cf. A002144, A006278, A236382, A341678.
%K A236381 nonn
%O A236381 1,3
%A A236381 _Colin Barker_, Jan 24 2014
%E A236381 a(23)-a(27) from _Jinyuan Wang_, Apr 30 2025