OFFSET
1,4
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Stephan Ramon Garcia, Elvis Kahoro, Florian Luca, Primitive root discrepancy for twin primes, arXiv:1705.02485 [math.NT], 2017.
MATHEMATICA
(EulerPhi[#-1] - EulerPhi[#+1]) &@ Select[Prime@ Range@ 310, PrimeQ[# + 2] &] (* Giovanni Resta, May 13 2017 *)
PROG
(PARI) lista(nn) = forprime(p=2, nn, if (isprime(p+2), print1(eulerphi(p-1)-eulerphi(p+1), ", ")));
CROSSREFS
KEYWORD
sign
AUTHOR
Michel Marcus, May 13 2017
STATUS
approved