OFFSET
1,2
COMMENTS
Count of numbers smaller than and coprime to p for primes p such that p + 2 is composite.
Subsequence of A006093.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..6970
MATHEMATICA
EulerPhi[#]&@Select[Prime@Range@80, !PrimeQ[# + 2] &] (* Vincenzo Librandi, Feb 09 2018 *)
PROG
(PARI) {forprime(p=2, 400, if(!isprime(p+2), print1(eulerphi(p), ", ")))} \\ Klaus Brockhaus, Aug 31 2008
(Magma) [EulerPhi(p): p in PrimesUpTo(400) | not IsPrime(p+2)]; // Vincenzo Librandi, Feb 09 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Teofilatto, Aug 11 2008
EXTENSIONS
Edited and a(1) = 1, a(12) = 66 inserted by Klaus Brockhaus, Aug 31 2008
STATUS
approved