

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 kth Pell number.


1



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
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..56.
Bernadette Faye, 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/(12*xx^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: A082182 A032719 A275287 * A045355 A252281 A165319
Adjacent sequences: A261578 A261579 A261580 * A261582 A261583 A261584


KEYWORD

nonn


AUTHOR

Michel Marcus, Aug 25 2015


STATUS

approved



