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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
OFFSET
1,1
COMMENTS
Corresponding values of sigma(p) of primes p from A158913.
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
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Feb 07 2012
STATUS
approved