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 A326403 #15 Sep 14 2019 16:39:46
%S A326403 1,20,35,143,194,208,740,1220,1299,1419,1803,1892,3705,3716,3843,5186,
%T A326403 5635,7868,10659,13634,13905,17948,18507,18914,18980,21007,25388,
%U A326403 25545,30380,31599,32304,34595,37820,47067,70394,73059,78064,87856,94874,105908,116963
%N A326403 Numbers k such that iphi(k) = iphi(k+1), where iphi(k) is an infinitary analog to the Euler totient function (A091732).
%H A326403 Amiram Eldar, <a href="/A326403/b326403.txt">Table of n, a(n) for n = 1..1000</a>
%e A326403 20 is in the sequence since iphi(20) = iphi(21) = 12.
%t A326403 f[p_, e_] := p^(2^(-1 + Position[Reverse @ IntegerDigits[e, 2], _?(# == 1 &)])); a[1] = 1; a[n_] := Times @@ (Flatten @(f @@@ FactorInteger[n]) - 1); a1 = 1; s = {}; Do[a2 = a[n]; If[a1 == a2, AppendTo[s, n - 1]]; a1 = a2, {n, 2, 10^5}]; s
%Y A326403 Cf. A001274, A091732, A287055, A293184, A301866.
%K A326403 nonn
%O A326403 1,2
%A A326403 _Amiram Eldar_, Sep 14 2019