OFFSET
1,1
LINKS
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
KEYWORD
nonn
AUTHOR
Michel Marcus, Aug 25 2015
STATUS
approved