A162281 - OEIS

A162281

Values of sigma_0(n) for n in A162279.

4, 4, 4, 4, 4, 8, 4, 8, 4, 4, 4, 4, 8, 4, 8, 4, 4, 8, 4, 4, 8, 12, 4, 8, 4, 8, 4, 4, 4, 8, 6, 4, 4, 8, 4, 8, 12, 4, 4, 4, 8, 4, 4, 4, 4, 8, 4, 8, 12, 4, 4, 8, 16, 4, 8, 12, 4, 8, 4, 6, 4, 4, 12, 4, 8, 4, 4, 8, 4, 12, 4, 8, 4, 8, 12, 4, 4, 8, 6, 4, 8, 16, 12, 4, 4, 4, 4, 8, 4, 12, 4, 8, 4, 4, 8, 4, 8, 12, 4, 8

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OFFSET

1,1

COMMENTS

No primes can appear in this sequence; to have sigma_0(n) = p, a prime, we must have n = q^{p-1} for some prime q, and each such n for fixed p will have a distinct value for sigma(n).

Conjecture: every composite number appears in this sequence. - Max Alekseyev

Up to sigma(n) = 500000, the only odd value is 9, for 106276 = 326^2 and 165649 = 407^2; these have sigma(n) = 187131.

LINKS

Table of n, a(n) for n=1..100.

Franklin T. Adams-Watters, Table of duplicate sigma values up to sigma(n) = 10000

FORMULA

a(n) = A000005(A162279(n)) = A000005(A162280(n)).

CROSSREFS

Cf. A000005, A162279.

Sequence in context: A085142 A064053 A108893 * A262690 A048760 A287392

Adjacent sequences: A162278 A162279 A162280 * A162282 A162283 A162284

KEYWORD

nonn

AUTHOR

Franklin T. Adams-Watters, Jun 29 2009

STATUS

approved