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A324216 Sequence lists numbers k > 1 such that k^4 == phi(k) (mod sigma(k)), where phi = A000010 and sigma = A000203. 2
2, 76, 782, 1836, 3996, 26754, 28896, 51240, 122598, 130734, 265524, 306204, 379350, 450846, 735012, 1132740, 1169472, 2120160, 2670974, 4095080, 4312440, 4421088, 8448120, 8693640, 9404160, 10113966, 10890978, 12710304, 12945312, 15328872, 16385376, 18028836 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..32.

FORMULA

Solutions of k^4 mod sigma(k) = phi(k).

EXAMPLE

sigma(76) = 140 and 76^4 mod 140 = 36 = phi(76).

MAPLE

with(numtheory): op(select(n->n^4 mod sigma(n)=phi(n), [$1..2670974]));

MATHEMATICA

Select[Range[2, 41*10^5], PowerMod[#, 4, DivisorSigma[1, #]]==EulerPhi[#]&] (* The program generates the first 20 terms of the sequence. *) (* Harvey P. Dale, Jul 09 2022 *)

CROSSREFS

Cf. A000010, A000203, A324214, A324215.

Sequence in context: A351433 A351376 A276203 * A198704 A198623 A198651

Adjacent sequences: A324213 A324214 A324215 * A324217 A324218 A324219

KEYWORD

nonn,easy

AUTHOR

Paolo P. Lava, Feb 18 2019

EXTENSIONS

a(23)-a(32) from Giovanni Resta, Feb 19 2019

STATUS

approved

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Last modified December 4 21:40 EST 2022. Contains 358570 sequences. (Running on oeis4.)