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A241480 Numbers such that the GCD of the x's that satisfy sigma(x)=sigma(n) is not equal to 1. 1
2, 3, 4, 5, 7, 8, 9, 12, 13, 18, 19, 22, 27, 29, 32, 36, 37, 43, 45, 48, 49, 50, 61, 64, 67, 68, 72, 73, 75, 80, 81, 82, 91, 98, 100, 101, 104, 106, 109, 116, 121, 122, 128, 129, 133, 134, 137, 144, 146, 148, 149, 152, 156, 157, 160, 162, 163, 169, 171, 173 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Apart from 1, all terms of A211656 belong here since the solutions to sigma(x)=sigma(n) form a singleton and thus their GCD is n itself.

LINKS

Table of n, a(n) for n=1..60.

FORMULA

Numbers such that A241479(n) is not equal to 1.

PROG

(PARI) sigv(n) =  select(i->sigma(i) == n, vector(n, i, i));

isok(n) = (gcd(sigv(sigma(n))) != 1);

CROSSREFS

Cf. A000203, A211656, A241479.

Sequence in context: A086753 A160519 A287927 * A211656 A051204 A335154

Adjacent sequences:  A241477 A241478 A241479 * A241481 A241482 A241483

KEYWORD

nonn

AUTHOR

Michel Marcus, Apr 23 2014

STATUS

approved

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Last modified April 16 18:53 EDT 2021. Contains 343050 sequences. (Running on oeis4.)