OFFSET
1,5
REFERENCES
Robert Israel, Posting to Sequence Fans Mailing List, Feb 06, 2011
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
MATHEMATICA
a[n_] := Sum[Boole[GCD[a, n] == 1 && GCD[b, n] == 1 && GCD[a, b] == 1], {a, 1, n-2}, {b, a+1, n-1}]; Array[a, 100] (* Jean-François Alcover, Mar 05 2019, from PARI *)
PROG
(PARI) a(n)=sum(a=1, n-2, sum(b=a+1, n-1, gcd(a, n)==1&&gcd(b, n)==1&&gcd(a, b)==1)) \\ Charles R Greathouse IV, Apr 28 2015
CROSSREFS
KEYWORD
nonn,look
AUTHOR
N. J. A. Sloane, Feb 07 2011
STATUS
approved