A294030 Values of bphi(k) = bphi(k+1), where bphi is the bi-unitary analog of Euler's totient function (A116550).

1, 9, 14, 42, 161, 161, 798, 1400, 86156, 123656, 419430, 387868, 508797, 772121, 870233, 4162866, 8754569, 126168912, 126991491, 128007618, 131491736

Offset

1,2

Comments

The bi-unitary totient function of numbers k such that k and k+1 have the same function value (A293184).

Links

Table of n, a(n) for n=1..21.

Formula

a(n) = A116550(A293184(n)).

Example

9 is in the sequence since 9 = bphi(14) = bphi(15).

Mathematica

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 *)

Crossrefs

The bi-unitary version of A003275.

Cf. A116550, A293184.

Sequence in context: A066793 A275508 A139055 * A079625 A027009 A239038

Adjacent sequences: A294027 A294028 A294029 * A294031 A294032 A294033

Keyword

nonn,more

Author

Amiram Eldar, Oct 22 2017

Extensions

a(10)-a(11) from Michel Marcus, Nov 14 2017

a(12)-a(21) from Amiram Eldar, Jul 16 2022

Status

approved