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A067890
Primes p such that phi(p+1) = phi(p-1).
3
5, 11, 71, 911, 1609, 2591, 4339, 15401, 58309, 59149, 80989, 208391, 215389, 496511, 589189, 1809079, 1970149, 3167569, 3260809, 3516109, 5914369, 9832271, 12231311, 13608071, 14470061, 16537151, 16692551, 19018369, 19462661
OFFSET
1,1
COMMENTS
Primes in A066812.
LINKS
FORMULA
a(n) = prime(A066902(n)). - Giovanni Resta, Apr 06 2020
MATHEMATICA
Select[Prime[Range[124*10^4]], EulerPhi[#-1]==EulerPhi[#+1]&] (* Harvey P. Dale, Apr 09 2019 *)
PROG
(PARI) v=[]; forprime(p=2, 40000000, if(eulerphi(p+1)==eulerphi(p-1), v=concat(v, p))); v
CROSSREFS
Sequence in context: A189802 A328453 A175207 * A303549 A192436 A154797
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Mar 02 2002
EXTENSIONS
More terms from Rick L. Shepherd, May 03 2002
STATUS
approved