A211876 Primes of the form Phi(phi(k),2), the phi(k)-th cyclotomic polynomial evaluated at 2, where phi is the Euler totient function.

3, 5, 11, 13, 17, 241, 257, 331, 683, 5419, 61681, 65537, 2796203, 15790321, 22366891, 4278255361, 4562284561, 77158673929, 1133836730401, 18446744069414584321, 291280009243618888211558641, 78919881726271091143763623681, 84159375948762099254554456081, 84179842077657862011867889681

Offset

1,1

Links

Table of n, a(n) for n=1..24.

Mathematica

s = Union[Table[EulerPhi[n], {n, 2000}]]; t = Union[Select[Table[ Cyclotomic[ n, 2], {n, s}], PrimeQ]]; Select[t, # < 10^30 &]

Prog

(PARI)
s=Set([]);
for (n=1, 10^3, my(a=polcyclo(eulerphi(n), 2)); if(ispseudoprime(a), s=setunion(s, [a])));
v211876=s  /* Joerg Arndt, Apr 13 2013 */

Crossrefs

Cf. A000010, A211875, A211874.

Sequence in context: A243627 A178604 A153443 * A066587 A047621 A239636

Adjacent sequences: A211873 A211874 A211875 * A211877 A211878 A211879

Keyword

nonn

Author

Alexander Gruber, Feb 12 2013

Status

approved