cp's OEIS Frontend

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.

A357326 Weird untouchable numbers.

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%I A357326 #13 Sep 28 2022 03:53:13
%S A357326 836,7192,7912,12670,13510,16030,16310,16870,17272,18830,21910,24290,
%T A357326 24430,26530,26810,29470,31430,34930,35210,35630,37870,42910,43330,
%U A357326 46130,46270,48370,52990,53830,57890,61810,70910,73430,74270,74410,76790,77630,79030,82670
%N A357326 Weird untouchable numbers.
%C A357326 Abundant numbers that are not the sum of any subset of their aliquot divisors, and are also not the sum of all the aliquot divisors of any other number.
%H A357326 Amiram Eldar, <a href="/A357326/b357326.txt">Table of n, a(n) for n = 1..3776</a>
%t A357326 weirdQ[n_] := Module[{d = Most[Divisors[n]]}, If[Total[d] <= n, False, SeriesCoefficient[Series[Product[1 + x^d[[i]], {i, Length[d]}], {x, 0, n}], n] == 0]]; seq[max_] := Module[{s = Table[0, {n, 1, max}], i}, Do[If[(i = DivisorSigma[1, n] - n) <= max, s[[i]]++], {n, 2, (max - 1)^2}]; Select[Position[s, 0] // Flatten, weirdQ]]; seq[8000]
%Y A357326 Intersection of A005114 and A006037.
%Y A357326 Cf. A001065, A005101.
%K A357326 nonn
%O A357326 1,1
%A A357326 _Amiram Eldar_, Sep 24 2022