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%I #14 Jul 16 2022 07:13:58
%S 1,9,14,42,161,161,798,1400,86156,123656,419430,387868,508797,772121,
%T 870233,4162866,8754569,126168912,126991491,128007618,131491736
%N Values of bphi(k) = bphi(k+1), where bphi is the bi-unitary analog of Euler's totient function (A116550).
%C The bi-unitary totient function of numbers k such that k and k+1 have the same function value (A293184).
%F a(n) = A116550(A293184(n)).
%e 9 is in the sequence since 9 = bphi(14) = bphi(15).
%t bphi[1] = 1; bphi[n_] := With[{pp = Power @@@ FactorInteger[n]}, Count[Range[n], m_ /; Intersection[pp, Power @@@ FactorInteger[m]] == {}]]; a={}; b1=0; Do[b2 = bphi[k]; If[b1 == b2, a = AppendTo[a, b1]]; b1 = b2, {k, 1, 10^2}]; a (* after _Jean-François Alcover_ at A116550 *)
%Y The bi-unitary version of A003275.
%Y Cf. A116550, A293184.
%K nonn,more
%O 1,2
%A _Amiram Eldar_, Oct 22 2017
%E a(10)-a(11) from _Michel Marcus_, Nov 14 2017
%E a(12)-a(21) from _Amiram Eldar_, Jul 16 2022
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