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A069552 Numbers n such that phi(n)=sigma(core(n)) where phi(x) is the Euler totient function, sigma(x) the sum of divisors of x and core(x) the squarefree part of x (the smallest integer such that x*core(x) is a square). 0
1, 12, 56, 140, 270, 630, 1672, 4180, 6426, 18810, 80104, 93496, 99484, 102856, 116116, 140296, 191862, 200260, 220616, 223938, 224536, 233740, 257140, 350740, 447678, 449442, 522522, 551540, 561340, 702240, 901170 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..31.

PROG

(PARI) for(n=1, 10^6, if(eulerphi(n)==sigma(core(n)), print1(n, ", ")))

CROSSREFS

Sequence in context: A009653 A133001 A104188 * A035005 A001386 A046998

Adjacent sequences:  A069549 A069550 A069551 * A069553 A069554 A069555

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Apr 17 2002

STATUS

approved

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Last modified January 17 10:21 EST 2019. Contains 319218 sequences. (Running on oeis4.)