OFFSET
0,4
EXAMPLE
a(5) = phi(1)*phi(2)*phi(4)*phi(6)*phi(10) = 1*1*2*2*4 = 16.
MAPLE
with(NumberTheory);
f:=n->mul(phi(ithprime(k)-1), k=1..n);
[seq(f(n), n=1..32)];
PROG
(PARI) a(n) = prod(k=1, n, eulerphi(prime(k)-1)); \\ Michel Marcus, Nov 04 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Marc LeBrun and N. J. A. Sloane, Nov 04 2020
STATUS
approved