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%I #9 Apr 09 2020 05:24:32
%S 1,168,194,350,1368,1628,3705,5186,5328,6929,7475,25545,26047,26864,
%T 28251,34936,37248,56724,65675,81732,82368,87308,87367,88450,91539,
%U 132308,164691,166624,244215,265524,280818,281897,388245,465651,501024,577524,806895,859901
%N Numbers k such that A173557(k) = A173557(k+1).
%C Kim et al. (2019) conjectured that A173557(k) = A173557(k+1) is divisible by 12 for all the terms k > 1.
%H Amiram Eldar, <a href="/A333874/b333874.txt">Table of n, a(n) for n = 1..712</a> (terms below 2*10^10)
%H Daeyeoul Kim, Umit Sarp, and Sebahattin Ikikardes, <a href="http://dx.doi.org/10.18514/MMN.2019.2470">Certain combinatoric convolution sums arising from Bernoulli and Euler Polynomials</a>, Miskolc Mathematical Notes, No. 20, Vol. 1 (2019): pp. 311-330.
%e 1 is a term since A173557(1) = A173557(2) = 1.
%t f[p_, e_] := p - 1; u[1] = 1; u[n_] := Times @@ (f @@@ FactorInteger[n]); s = {}; u1 = 1; Do[u2 = u[n]; If[u1 == u2, AppendTo[s, n-1]]; u1 = u2, {n, 2, 10^5}]; s
%Y Cf. A001274, A173557, A333875.
%K nonn
%O 1,2
%A _Amiram Eldar_, Apr 08 2020