A090869 Irregular primes whose indices are irregular primes of order one.

613, 877, 1117, 1721, 1753, 2153, 2557, 2671, 4349, 4943, 5039, 5179, 5443, 5641, 5939, 6037, 6827, 6997, 7591, 7853, 8069, 8209, 8527, 8669, 9221, 9311, 9377, 9859, 10729, 11149, 11353, 11503, 11933, 12211, 12413, 12743, 12923, 13001, 13037, 13367, 13693, 13729, 13999, 14369, 14449, 14551, 14759, 15541, 15923, 16141

Offset

1,1

Comments

This sequence is infinite.

Links

Table of n, a(n) for n=1..50.

Cino Hilliard, file irregprimes.txt [Feb 13, 2004, cached from Yahoo group B2LCC/files/Bernoulli/]

Mohammad Amin Shokrollahi, Tables [broken, empty document]

Example

37 is the first irregular prime, 613 is the 37th irregular prime, i.e., iprime(iprime(1)) = 613, so 613 is a member.

Prog

(PARI) \\ Irregular prime-indexed primes. Download the linked file (e.g. with "wget https://oeis.org/a090869.txt") into the gp working directory, and start a new PARI session.
iprime = readvec("your_path/a090869.txt");
ipips(n) = for(x=1, n, y=iprime[iprime[x]]; print1(y ", "));
ipips(50) \\ Michel Marcus, Georg Fischer Nov 14 2019

Crossrefs

Cf. A000928 (irregular primes).

Sequence in context: A159641 A100364 A142435 * A020372 A032657 A117503

Adjacent sequences: A090866 A090867 A090868 * A090870 A090871 A090872

Keyword

easy,nonn

Author

Cino Hilliard, Feb 12 2004

Status

approved