A039781 Numbers k such that phi(k) is equal to A008473(k+1).

55, 174, 183, 341, 407, 1274, 5424, 6887, 18903, 22167, 27559, 53847, 66711, 68237, 77957, 78155, 91524, 132791, 133574, 138471, 149435, 191575, 220759, 274224, 339024, 413424, 432233, 493724, 505735, 543221, 684167, 694823, 703824, 711774, 747175, 883463

Offset

1,1

Links

Table of n, a(n) for n=1..36.

Example

phi(174)=56, 175=5^2*7^1, (5+2)*(7+1)=56.

Prog

(PARI) b(n)=my(f = factor(n)); for (k=1, #f~, f[k, 1] = f[k, 1] + f[k, 2]; f[k, 2] = 1; ); factorback(f); \\ A008473
isok(k) = eulerphi(k) == b(k+1); \\ Michel Marcus, Feb 25 2021

Crossrefs

Cf. A000010, A008473.

Cf. A039779, A039780.

Sequence in context: A276050 A256353 A068641 * A135657 A178793 A334531

Adjacent sequences: A039778 A039779 A039780 * A039782 A039783 A039784

Keyword

nonn

Author

Olivier Gérard

Extensions

Title corrected and more terms from Sean A. Irvine, Feb 24 2021

Status

approved