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 A131903 #8 Apr 03 2015 03:47:32
%S A131903 3,5,7,8,9,10,11,13,14,15,17,18,19,20,21,22,23,25,26,27,28,29,30,31,
%T A131903 32,33,34,35,37,38,39,40,41,42,43,44,45,46,47,49,50,51,52,53,54,55,56,
%U A131903 57,58,59,61,62,63,65,66,67,68,69,70,71,72,73,74,75,76,77,78
%N A131903 Integers x such that d(k)=d(x) for some 0<k<x, where d=A000005 is the number of divisors.
%C A131903 Complement of A007416. - _T. D. Noe_, Jul 26 2007
%F A131903 a(n) = n-th element of the set {x>0 : there exists a k with 0<k<x and d(k)=d(x)}, where d=A000005 is the number of divisors.
%e A131903 This sequence contains 8 because 8 has |{1,2,4,8}|=4 divisors and 6<8 has |{1,2,3,6}|=4 divisors.
%t A131903 Clear[tmp]; Function[n, If[Head[ #1] === tmp, #1 = n; Unevaluated[Sequence[]], n] & [tmp[DivisorSigma[0, n]]]] /@ Range[64]
%o A131903 (PARI) isok(n) = {my(nd = numdiv(n)); for (k=1, n-1, if (numdiv(k) == nd, return (1)););}
%Y A131903 Cf. A069822, A131902-A131908.
%K A131903 easy,nonn
%O A131903 1,1
%A A131903 Peter Pein (petsie(AT)dordos.net), Jul 26 2007
%E A131903 a(54)-a(67) from _Michel Marcus_, Apr 03 2015
%E A131903 Edited by _Danny Rorabaugh_, Apr 03 2015