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A090869
Irregular primes whose indices are irregular primes of order one.
1
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
Cino Hilliard, file irregprimes.txt, Feb 13, 2004. [cached from Yahoo group B2LCC/files/Bernoulli/]
Mohammad Amin Shokrollahi, Tables.
FORMULA
a(n) = A000928(A000928(n)). - Amiram Eldar, Jul 02 2024
EXAMPLE
37 is the first irregular prime, 613 is the 37th irregular prime, i.e., iprime(iprime(1)) = 613, so a(1) = 613.
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
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Feb 12 2004
STATUS
approved