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 A326181 #22 Jun 17 2019 13:13:46
%S A326181 54,56,87,95,276,308,429,446,455,501,581,611,158928,194928,195072,
%T A326181 199950,226352,234608,236432,248325,255678,263504,266192,273050,
%U A326181 275415,304575,336903,341162,353675,366575,369425,369843,380463,386313,389463,406565,411725,415925,422303,447587,468743,497333,500993,511829,515267,519557,519677
%N A326181 Numbers n for which sigma(sigma(n)) = 3*sigma(n).
%C A326181 Any odd perfect numbers must occur in this sequence, as such numbers must be in the intersection of A000396 and A326051, that is, satisfy both sigma(n) = 2n and sigma(2n) = 6n = 3*2n, thus in combination they must satisfy sigma(sigma(n)) = 3*sigma(n). Note that odd perfect numbers should occur also in A019283.
%C A326181 If, as conjectured, A005820 has 6 terms, then this sequence is finite and has 756 terms. - _Giovanni Resta_, Jun 17 2019
%H A326181 Giovanni Resta, <a href="/A326181/b326181.txt">Table of n, a(n) for n = 1..756</a> (first 169 terms from Antti Karttunen)
%H A326181 <a href="/index/O#opnseqs">Index entries for sequences where any odd perfect numbers must occur</a>
%o A326181 (PARI) isA326181(n) = { my(s=sigma(n)); (sigma(s)==3*s); };
%Y A326181 Cf. A000203, A000396, A005820, A019283, A051027, A087943, A272027 (3*sigma(n)), A326051.
%Y A326181 Subsequence of A066961.
%K A326181 nonn
%O A326181 1,1
%A A326181 _Antti Karttunen_, Jun 16 2019