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.

A337382 Numbers k for which A003973(k) < 2*sigma(k).

This page as a plain text file.
%I A337382 #7 Aug 27 2020 17:08:42
%S A337382 1,2,3,4,5,7,10,11,13,17,19,22,23,25,26,29,31,33,34,37,38,39,41,43,46,
%T A337382 47,51,53,55,57,58,59,61,62,65,67,69,71,73,74,77,79,82,83,85,86,87,89,
%U A337382 91,93,94,95,97,101,103,106,107,109,111,113,115,116,118,119,121,122,123,127,129,131,133,134,137,139,141
%N A337382 Numbers k for which A003973(k) < 2*sigma(k).
%H A337382 Antti Karttunen, <a href="/A337382/b337382.txt">Table of n, a(n) for n = 1..20000</a>
%H A337382 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%H A337382 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%o A337382 (PARI)
%o A337382 A003973(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); sigma(factorback(f)); };
%o A337382 isA337382(n) = (A003973(n)<2*sigma(n));
%Y A337382 Cf. A000203, A003961, A003973.
%Y A337382 Cf. A337381 (complement).
%Y A337382 Positions of zeros in A337383.
%Y A337382 Subsequence of A337379.
%Y A337382 Cf. also A246281.
%K A337382 nonn
%O A337382 1,2
%A A337382 _Antti Karttunen_, Aug 27 2020