A067386 - OEIS

A067386

Primes p such that p+1 and p-1 have the same number of distinct prime factors.

3, 11, 13, 19, 23, 37, 47, 53, 73, 97, 107, 131, 139, 163, 181, 193, 229, 239, 281, 307, 311, 349, 373, 379, 383, 409, 439, 443, 487, 491, 521, 577, 599, 601, 617, 619, 643, 683, 701, 709, 727, 739, 743, 761, 811, 821, 827, 829, 853, 863, 881, 883, 919, 937

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

MAPLE

q:= p-> isprime(p) and nops(ifactors(p+1)[2])=nops(ifactors(p-1)[2]):

select(q, [$1..1000])[]; # Alois P. Heinz, May 08 2022

MATHEMATICA

Select[Prime[Range[200]], PrimeNu[#-1]==PrimeNu[#+1]&] (* Harvey P. Dale, Jun 28 2020 *)

PROG

(PARI) is(n)=omega(n-1)==omega(n+1) && isprime(n) \\ Charles R Greathouse IV, Sep 14 2015