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A103665 Primes p such that the number of divisors of p-1 is greater than the number of divisors of p+1. 7
13, 31, 37, 43, 61, 67, 73, 97, 101, 109, 113, 127, 151, 157, 163, 181, 193, 211, 229, 241, 257, 271, 277, 281, 283, 313, 331, 337, 353, 373, 379, 397, 401, 409, 421, 433, 457, 463, 487, 521, 523, 541, 547, 571, 577, 601, 613, 617, 631, 641, 661, 673, 677 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Mathematica coding by Wouter Meeussen and Robert G. Wilson v.

LINKS

Hugo Pfoertner, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1)=13 because d(12)=6 > d(14)=4.

MATHEMATICA

Select[Prime[Range[2, 140]], Length[Divisors[ # - 1]] > Length[Divisors[ # + 1]] &]

PROG

(PARI)

forprime (k=2, 700, if(numdiv(k-1)>numdiv(k+1), print1(k, ", ")))

\\ Hugo Pfoertner, Nov 30 2017

CROSSREFS

Cf. A008328 number of divisors of p-1, A008329 number of divisors of p+1, A103664, A103666, A103667.

Sequence in context: A046414 A023694 A038465 * A040050 A040086 A176181

Adjacent sequences:  A103662 A103663 A103664 * A103666 A103667 A103668

KEYWORD

nonn

AUTHOR

Hugo Pfoertner, Feb 19 2005

STATUS

approved

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Last modified August 3 05:37 EDT 2020. Contains 336197 sequences. (Running on oeis4.)