A261581 Primes such that z(p) is not divisible by 4 where z(n) is A214028(n), the smallest k such that n divides A000129(k), the k-th Pell number.

2, 5, 7, 13, 23, 29, 31, 37, 41, 47, 53, 61, 71, 79, 101, 103, 109, 127, 137, 149, 151, 157, 167, 173, 181, 191, 197, 199, 223, 229, 239, 263, 269, 271, 277, 293, 311, 313, 317, 349, 353, 359, 367, 373, 383, 389, 397, 409, 421, 431, 439, 457, 461, 463, 479, 487

Offset

1,1

Links

Table of n, a(n) for n=1..56.

Bernadette Faye and Florian Luca, Pell Numbers whose Euler Function is a Pell Number, arXiv:1508.05714 [math.NT], 2015.

Example

The smallest Pell number divisible by the prime 2 has index 2, which is not divisible by 4, so 2 is in the sequence.

Prog

(PARI) pell(n) = polcoeff(Vec(x/(1-2*x-x^2) + O(x^(n+1))), n);
z(n) = {k=1; while (pell(k) % n, k++); k; }
lista(nn) = {forprime(p=2, nn, if (z(p) % 4, print1(p, ", ")); ); }

Crossrefs

Cf. A000129, A214028, A261580.

Sequence in context: A032719 A334246 A275287 * A045355 A252281 A165319

Adjacent sequences: A261578 A261579 A261580 * A261582 A261583 A261584

Keyword

nonn

Author

Michel Marcus, Aug 25 2015

Status

approved