A324216 Sequence lists numbers k > 1 such that k^4 == phi(k) (mod sigma(k)), where phi = A000010 and sigma = A000203.

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

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