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 A290504 #18 Dec 30 2019 14:42:42
%S A290504 3814697265625,7629394531250,11444091796875,15258789062500,
%T A290504 22888183593750,26702880859375,30517578125000,34332275390625,
%U A290504 41961669921875,45776367187500,53405761718750,61035156250000,68664550781250,72479248046875,80108642578125,83923339843750
%N A290504 Hypotenuses for which there exist exactly 18 distinct integer triangles.
%C A290504 Numbers whose square is decomposable in 18 different ways into the sum of two nonzero squares: these are those with only one prime divisor of the form 4k+1 with multiplicity eighteen.
%H A290504 Ray Chandler, <a href="/A290504/b290504.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Hamdi Sahloul)
%F A290504 Terms are obtained by the product A004144(k)*A002144(p)^18 for k, p > 0 ordered by increasing values.
%e A290504 a(1) = 3814697265625 = 5^18, a(5) = 22888183593750 = 2*3*5^18, a(101) = 732421875000000 = 2^6*3*5^18.
%t A290504 r[a_]:={b, c}/.{ToRules[Reduce[0<b<c && a^2 == b^2 + c^2, {b, c}, Integers]]}; Select[Range[732421875000000], Length[r[#]] == 18 &] (* _Vincenzo Librandi_, Mar 01 2016 *)
%Y A290504 Cf. A002144, A006339, A046080, A046109, A083025.
%Y A290504 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), A290503 (15), A097238 (16), A097239 (17), A290505 (19), A097103 (22), A097244 (31), A097245 (37), A097282 (40), A097626 (67).
%K A290504 nonn
%O A290504 1,1
%A A290504 _Hamdi Sahloul_, Aug 04 2017