The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

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