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 A290503 #18 Dec 30 2019 14:38:46
%S A290503 30517578125,61035156250,91552734375,122070312500,183105468750,
%T A290503 213623046875,244140625000,274658203125,335693359375,366210937500,
%U A290503 427246093750,488281250000,549316406250,579833984375,640869140625,671386718750,701904296875,732421875000
%N A290503 Hypotenuses for which there exist exactly 15 distinct integer triangles.
%C A290503 Numbers whose square is decomposable in 15 different ways into the sum of two nonzero squares: these are those with only one prime divisor of the form 4k+1 with multiplicity fifteen.
%H A290503 Ray Chandler, <a href="/A290503/b290503.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Hamdi Sahloul)
%F A290503 Terms are obtained by the product A004144(k)*A002144(p)^15 for k, p > 0 ordered by increasing values.
%e A290503 a(1) = 30517578125 = 5^15, a(5) = 183105468750 = 2*3*5^15, a(101) = 5859375000000 = 2^6*3*5^15.
%t A290503 r[a_]:={b, c}/.{ToRules[Reduce[0<b<c && a^2 == b^2 + c^2, {b, c}, Integers]]}; Select[Range[5859375000000], Length[r[#]] == 15 &] (* _Vincenzo Librandi_, Mar 01 2016 *)
%Y A290503 Cf. A002144, A006339, A046080, A046109, A083025.
%Y A290503 Cf. A004144 (0), A084645 (1), A084646 (2), A084647 (3), A084648 (4), A084649 (5), A097219 (6), A097101 (7), A290499 (8), A290500 (9), A097225 (10), A290501 (11), A097226 (12), A097102 (13), A290502 (14), A097238 (16), A097239 (17), A290504 (18), A290505 (19), A097103 (22), A097244 (31), A097245 (37), A097282 (40), A097626 (67).
%K A290503 nonn
%O A290503 1,1
%A A290503 _Hamdi Sahloul_, Aug 04 2017