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

Author

Amiram Eldar, Oct 22 2017

Keywords

• nonn
• more

Comments

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

Examples

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

Crossrefs

The bi-unitary version of A003275.

Cf. A116550, A293184.

Programs

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 *)

Formula

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

Extensions

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

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