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 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. 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS 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/(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

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Last modified September 29 21:59 EDT 2020. Contains 337432 sequences. (Running on oeis4.)