login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A164319 Primes p such that the sum of divisors of p+1 is larger than 2*p. 2
3, 5, 7, 11, 17, 19, 23, 29, 31, 41, 47, 53, 59, 71, 79, 83, 89, 101, 103, 107, 113, 127, 131, 137, 139, 149, 167, 173, 179, 191, 197, 199, 223, 227, 233, 239, 251, 257, 263, 269, 271, 281, 293, 307, 311, 317, 347, 349, 353, 359, 367, 379, 383, 389, 401, 419 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For a subset of these, namely p=179, 239, 359, 419, etc, sigma(p+1) is even larger than 3*p.

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..5000

EXAMPLE

For p=3, the sum of divisors of p+1 is A000203(4)=7 > 2*3, so p=3 is in the sequence.

MATHEMATICA

f[n_]:=Plus@@Divisors[n]; lst={}; Do[p=Prime[n]; If[f[p+1]>2*p, AppendTo[lst, p]], {n, 6!}]; lst

Select[Prime[Range[100]], DivisorSigma[1, # + 1] > 2 # &] (* G. C. Greubel, Sep 13 2017 *)

PROG

(PARI) lista(nn) = forprime(p=2, nn, if (sigma(p+1) > 2*p, print1(p, ", "))); \\ Michel Marcus, Sep 13 2017

CROSSREFS

Cf. A008333, A085498, A164318.

Sequence in context: A116959 A249505 A091305 * A085498 A225223 A226653

Adjacent sequences:  A164316 A164317 A164318 * A164320 A164321 A164322

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Aug 12 2009

EXTENSIONS

Edited by R. J. Mathar, Aug 21 2009

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 25 05:41 EDT 2019. Contains 324346 sequences. (Running on oeis4.)