A338364 a(n) = Product_{k=1..n} phi(prime(k)-1).

1, 1, 1, 2, 4, 16, 64, 512, 3072, 30720, 368640, 2949120, 35389440, 566231040, 6794772480, 149484994560, 3587639869440, 100453916344320, 1607262661509120, 32145253230182400, 771486077524377600, 18515665860585062400, 444375980654041497600, 17775039226161659904000

Offset

0,4

Links

Table of n, a(n) for n=0..23.

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

Cf. A000010, A008330, A002110.

Sequence in context: A153998 A154001 A154004 * A060656 A271234 A061286

Adjacent sequences: A338361 A338362 A338363 * A338365 A338366 A338367

Keyword

nonn

Author

Marc LeBrun and N. J. A. Sloane, Nov 04 2020

Status

approved