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A067386
Primes p such that p+1 and p-1 have the same number of distinct prime factors.
4
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
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
CROSSREFS
Cf. A115103 (same number of prime factors with multiplicity).
Sequence in context: A191049 A373471 A103835 * A063621 A176870 A089152
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Feb 23 2002
STATUS
approved