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

Author

Michel Marcus, Aug 25 2015

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Cf. A000129, A214028, A261580.

Programs

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, ", ")););}