cp's OEIS Frontend

A162284 Odd numbers n such that b(n) >= n and b(b(n)) >= n, where b(n) = A161942(n) = oddpart(sigma(n)).

%I A162284 #14 Nov 30 2024 23:46:49
%S A162284 1,81,18966025,135187129,164275489,350561925,445421025,598047025,
%T A162284 649587169,748733769,850830561,960362325,1055925025,1341097641,
%U A162284 1406175001,1476326929,1520766009,1536248025,1591004025,1735566525
%N A162284 Odd numbers n such that b(n) >= n and b(b(n)) >= n, where b(n) = A161942(n) = oddpart(sigma(n)).
%C A162284 Applying b a third time produces a smaller value for every number in this sequence up to 10^10, except 1.
%C A162284 Of the first 43 terms, only the following nine are not squares: 350561925, 960362325, 1591004025, 1735566525, 1753206525, 1831175325, 4558583925, 6745097205, 8766517725, and incidentally, all of them are terms of A228058. - _Antti Karttunen_, Jun 16 2019
%C A162284 But see also comments in A348743. - _Antti Karttunen_, Nov 30 2024
%H A162284 Robert Gerbicz, <a href="/A162284/b162284.txt">Table of n,a(n) up to 10^10; n=1..43</a>
%H A162284 <a href="/index/O#opnseqs">Index entries for sequences where any odd perfect numbers must occur</a>
%Y A162284 Cf. A161942, A228058, A326042.
%Y A162284 Subsequence of A348742.
%Y A162284 Cf. also A348743.
%K A162284 nonn
%O A162284 1,2
%A A162284 _Franklin T. Adams-Watters_, Jun 29 2009
%E A162284 Values for n > 3 from _Robert Gerbicz_