OFFSET
1,2
LINKS
Michel Marcus, Table of n, a(n) for n = 1..5000
FORMULA
EXAMPLE
a(3) = phi(6) = 2.
MAPLE
with(numtheory):with(combinat):a:=n->phi(binomial(n, 2)): seq(a(n), n=2..31); # Zerinvary Lajos, Oct 05 2007
MATHEMATICA
EulerPhi[Accumulate[Range[70]]] (* Harvey P. Dale, Sep 16 2012 *)
PROG
(PARI) vector(66, n, eulerphi(n*(n+1)/2))
(Sage) [euler_phi(binomial(n, 2)) for n in range(2, 32)] # Zerinvary Lajos, Jun 06 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Jon Perry, Jul 28 2003
STATUS
approved