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 A290499 #22 Dec 30 2019 14:14:23
%S A290499 390625,781250,1171875,1562500,2343750,2734375,3125000,3515625,
%T A290499 4296875,4687500,5468750,6250000,7031250,7421875,8203125,8593750,
%U A290499 8984375,9375000,10546875,10937500,12109375,12500000,12890625,14062500,14843750,16406250,16796875,17187500
%N A290499 Hypotenuses for which there exist exactly 8 distinct integer triangles.
%C A290499 Numbers whose square is decomposable in 8 different ways into the sum of two nonzero squares: these are those with only one prime divisor of the form 4k+1 with multiplicity eight.
%H A290499 Ray Chandler, <a href="/A290499/b290499.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Hamdi Sahloul)
%F A290499 Terms are obtained by the product A004144(k)*A002144(p)^8 for k, p > 0 ordered by increasing values.
%e A290499 a(1) = 390625 = 5^8, a(5) = 2343750 = 2*3*5^8, a(101) = 75000000 = 2^6*3*5^8.
%t A290499 r[a_]:={b, c}/.{ToRules[Reduce[0<b<c && a^2 == b^2 + c^2, {b, c}, Integers]]}; Select[Range[75000000], Length[r[#]] == 8 &] (* _Vincenzo Librandi_, Mar 01 2016 *)
%Y A290499 Cf. A002144, A006339, A046080, A046109, A083025.
%Y A290499 Cf. A004144 (0), A084645 (1), A084646 (2), A084647 (3), A084648 (4), A084649 (5), A097219 (6), A097101 (7), A290500 (9), A097225 (10), A290501 (11), A097226 (12), A097102 (13), A290502 (14), A290503 (15), A097238 (16), A097239 (17), A290504 (18), A290505 (19), A097103 (22), A097244 (31), A097245 (37), A097282 (40), A097626 (67).
%K A290499 nonn
%O A290499 1,1
%A A290499 _Hamdi Sahloul_, Aug 04 2017