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 A376256 #69 Mar 30 2025 06:31:49
%S A376256 1,2,4,8,12,16,48,72,128,240,432,576,720,1200,1728,1800,6912,10368,
%T A376256 15552,27648,32768,41472,67392,142560,184320,272160,326592,712800,
%U A376256 1140480,1190400,1658880,3345408,3571200,5702400,6220800,10222080,14859936,29719872,40255488,50319360,113218560,118879488
%N A376256 Numbers which are the minimum of a cycle in the map x -> phi(sigma(x)).
%C A376256 No further terms < 254731536.
%C A376256 The status of 254731536 is unknown, but conjectured not a term.
%C A376256 Additional terms include 2142720000, 5033164800, 150493593600, 3852635996160.
%C A376256 See further cycles in the linked document here below which contains 422 cycles. It includes the 80 cycles complied by Jud McCrainie in a linked document at A095955.
%H A376256 Richard R. Forberg, <a href="/A376256/a376256_2.pdf">The Prevalence of Cycles vs. "Unruly Events" from 10^8 to 10^55 after Iterating on n <- phi(sigma(n))</a>
%H A376256 Richard R. Forberg, <a href="/A376256/a376256_1.txt">422 Phi Sigma Cycles Organized by Length</a>
%o A376256 (PARI) \\ Naive program, assumes eventual termination (ok upto 254731535).
%o A376256 isok(n)={my(M=Map(),p=n); while(!mapisdefined(M,p) && p>=n, mapput(M,p,1); p=eulerphi(sigma(p))); p==n} \\ _Andrew Howroyd_, Sep 19 2024
%Y A376256 Union of A001229, A373435, A373453, A373454, etc.
%Y A376256 Cf. A062401, A095955.
%K A376256 nonn
%O A376256 1,2
%A A376256 _Richard R. Forberg_, Sep 16 2024