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 A211510 #22 Jan 27 2020 13:25:39
%S A211510 0,0,0,0,3,0,1,6,5,4,13,0,16,12,7,8,22,10,27,20,20,8,41,14,27,32,21,
%T A211510 36,66,0,28,38,40,36,71,12,53,60,57,16,83,14,80,60,32,64,75,50,98,62,
%U A211510 47,16,144,36,100,88,53,52,153,36,94,76,91,98,129,20,92,124,102
%N A211510 Number of ordered triples (w,x,y) with all terms in {1,...,n} and w^2 = x*y - 2n.
%C A211510 For a guide to related sequences, see A211422.
%C A211510 The original name was "... and w^2 = x*y + 2n", but this would yield 2 instead of 0 for a(3), as observed by _Pontus von Brömssen_. The corresponding sequence seems not to be in the OEIS yet. - _M. F. Hasler_, Jan 26 2020
%H A211510 Pontus von Brömssen, <a href="/A211510/b211510.txt">Table of n, a(n) for n = 0..1024</a>
%e A211510 From _Bernard Schott_, Jan 26 2020: (Start)
%e A211510 For n = 4, there are 3 ordered solutions with (1,3,3), (2,3,4) and (2,4,3) so a(4) = 3.
%e A211510 For n = 5, there is no solution, hence a(5) = 0.
%e A211510 The only solution for n = 6 is (2,4,4) with 2^2 = 4*4 - 2*6, hence a(6) = 1. (End)
%t A211510 t[n_] := t[n] = Flatten[Table[w^2 - x*y + 2 n, {w, 1, n}, {x, 1, n}, {y, 1, n}]]
%t A211510 c[n_] := Count[t[n], 0]
%t A211510 t = Table[c[n], {n, 0, 70}] (* A211510 *)
%o A211510 (Python)
%o A211510 import sympy
%o A211510 def A211510(n): return sum(x<=n and x*n>=w**2+2*n for w in range(1,n+1) for x in sympy.divisors(w**2+2*n)) # _Pontus von Brömssen_, Jan 26 2020
%o A211510 (PARI) apply( {A211510(n)=sum(w=1,n-2,my(w2n=(w^2-1)\n+2,s); fordiv(w^2+2*n,x, x>w2n||next; x>n&&break; s++);s)}, [1..100]) \\ _M. F. Hasler_, Jan 26 2020
%Y A211510 Cf. A211422.
%K A211510 nonn
%O A211510 0,5
%A A211510 _Clark Kimberling_, Apr 14 2012
%E A211510 Name corrected by _Pontus von Brömssen_, Jan 26 2020