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 A053990 #7 Jul 02 2025 16:01:59
%S A053990 0,12,24,40,60,72,84,112,120,144,180,220,240,252,264,312,336,360,364,
%T A053990 420,432,480,504,540,544,600,612,660,672,684,760,792,840,864,924,936,
%U A053990 1012,1080,1092,1104,1120,1200,1260,1300,1320,1404,1440,1512,1584,1624
%N A053990 Numbers of the form x*(x + 1)*y*(y + 1) ("bipronics") where x and y are distinct.
%e A053990 Taking x=1, y=2 gives 2 * 6 =12
%t A053990 bipr[{a_,b_}]:=a(a+1)b(b+1); Take[Union[bipr/@Subsets[Range[0,40], {2}]],50] (* _Harvey P. Dale_, Jun 01 2012 *)
%Y A053990 Cf. A054731, A054734, A072389.
%K A053990 nonn,easy
%O A053990 1,2
%A A053990 Stuart M. Ellerstein (ellerstein(AT)aol.com), Apr 04 2000
%E A053990 More terms from _James Sellers_, Apr 22 2000