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 A291453 #10 Aug 27 2017 23:45:34
%S A291453 0,2,3,4,5,6,7,8,9,11,13,15,16,17,18,21,24,25,26,28,31,32,34,36,38,44,
%T A291453 50,51,61,66,68,73,79,83,86,87,95,132,138,139,144,159,162,167,177,183,
%U A291453 188,189,191,194,213,230,242,253,255,265,273,274,277,287,300,310,311,337,338,352
%N A291453 Numbers n such that A291356(n) > 0.
%C A291453 Searching until n = 2500, we have found only 11 values of n with more than one solution to usigma(x) = prime(n)#: 8, 11, 13, 17, 24, 38, 86 have 2 solutions and 3, 5, 6, 7 have 3 solutions. Are these the only numbers with more than one solution?
%e A291453 For n = 6 there are 3 solutions: usigma(20018) = usigma(29504) = usigma(30029) = 30030 = A002110(6).
%t A291453 primorial[n_] := Product[Prime[i], {i, n}]; a[k_] := Module[{n = primorial[k], m = 1}, s = {};
%t A291453 If[PrimePowerQ[n - 1], AppendTo[s, n - 1]];
%t A291453 While[2^m<n, If[Divisible[n, 2^m + 1], r = n/(2^m + 1) - 1;
%t A291453 If[PrimePowerQ[r], AppendTo[s, 2^m*r]]]; m++]; Length[s]];
%t A291453 seq=Map[a,Range[1000]];Flatten[Position[seq,_?(#>0 &)]]
%Y A291453 Cf. A291356.
%K A291453 nonn
%O A291453 1,2
%A A291453 _Amiram Eldar_ and _Altug Alkan_, Aug 24 2017