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A206449 Values of sigma(p) of primes p such that sigma(p) = sigma(c) has solution for some composite number c. 0
12, 18, 24, 32, 42, 48, 54, 60, 72, 80, 84, 90, 98, 104, 108, 114, 128, 132, 140, 152, 168, 180, 182, 192, 224, 228, 234, 240, 252, 264, 270, 272, 294, 308, 312, 360, 384, 390, 420, 432, 434, 440, 444, 450, 468, 480, 492, 504, 522, 558, 570, 572, 588, 594, 600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding values of sigma(p) of primes p from A158913.

LINKS

Table of n, a(n) for n=1..55.

FORMULA

a(n) = A158913(n) + 1.

MATHEMATICA

Union@ Select[ DivisorSigma[1, Select[ Range@ 100, !PrimeQ@# &]], PrimeQ[# - 1] &] (* Robert G. Wilson v, Feb 09 2012 *)

CROSSREFS

Cf. A158913 (primes p such that there is a composite c with sigma(p)=sigma(c)), A206448 (values of sigma(c) of composite numbers c such that sigma(c) = sigma(d) has solution for any other composite number d), A000203.

Sequence in context: A258914 A241646 A181941 * A241852 A113756 A055482

Adjacent sequences:  A206446 A206447 A206448 * A206450 A206451 A206452

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Feb 07 2012

STATUS

approved

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Last modified July 31 05:53 EDT 2021. Contains 346367 sequences. (Running on oeis4.)