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A323333 The Euler phi function values of the powerful numbers, A000010(A001694(n)). 3
1, 2, 4, 6, 8, 20, 18, 16, 12, 42, 32, 24, 54, 40, 36, 110, 100, 64, 48, 156, 84, 80, 72, 120, 162, 128, 96, 272, 108, 294, 342, 168, 160, 144, 252, 220, 200, 256, 506, 192, 500, 216, 360, 312, 486, 336, 320, 812, 288, 240, 930, 440, 324, 400, 512, 660, 600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The sum of the reciprocals of all the terms of this sequence is Murata's constant Product_{p prime}(1 + 1/(p-1)^2) (A065485).

Sequence is injective: no value occurs more than once. - Amiram Eldar and Antti Karttunen, Sep 30 2019

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

Eckford Cohen, A property of Dedekind's psi-function, Proceedings of the American Mathematical Society, Vol. 12, No. 6 (1961), p. 996.

MATHEMATICA

EulerPhi /@ Join[{1}, Select[Range@ 1200, Min@ FactorInteger[#][[All, 2]] > 1 &]] (* after Harvey P. Dale at A001694 *)

PROG

(PARI) lista(nn) = apply(x->eulerphi(x), select(x->ispowerful(x), vector(nn, k, k))); \\ Michel Marcus, Jan 11 2019

CROSSREFS

Cf. A000010, A001694, A002618 (a subsequence), A065485, A082695, A112526, A323332.

Sequence in context: A152491 A329738 A133296 * A076402 A053198 A249278

Adjacent sequences:  A323330 A323331 A323332 * A323334 A323335 A323336

KEYWORD

nonn

AUTHOR

Amiram Eldar, Jan 11 2019

STATUS

approved

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Last modified May 7 09:10 EDT 2021. Contains 343636 sequences. (Running on oeis4.)