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 A215820 Odd numbers n such that the Fibonacci number F(n) can be written in the form a^2 + 2*b^2. 3
 1, 3, 9, 11, 13, 23, 25, 33, 39, 47, 59, 61, 71, 83, 107, 109, 121, 131, 141, 157, 167, 179, 183, 191, 193, 227, 249, 251, 299, 321, 337, 359, 363, 383, 393, 397, 423, 431, 433, 471, 501, 517, 579, 587, 601, 647, 649, 877, 911, 913, 947, 1079, 1091, 1093 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS These Fibonacci numbers F(n) have no prime factor congruent to 5 or 7 mod 8 to an odd power. LINKS Table of n, a(n) for n=1..54. Blair Kelly, Fibonacci and Lucas factorizations PROG (PARI) for(i=2, 500, a=factorint(fibonacci(i))~; has=0; for(j=1, #a, if(a[1, j]%8>4&&a[2, j]%2==1, has=1; break)); if(has==0&&i%2==1, print(i", "))) CROSSREFS Cf. A000045, A215818, A215819, A215821. Sequence in context: A287333 A174813 A116444 * A065136 A075720 A106373 Adjacent sequences: A215817 A215818 A215819 * A215821 A215822 A215823 KEYWORD nonn AUTHOR V. Raman, Aug 23 2012 EXTENSIONS 1 added by T. D. Noe, Aug 27 2012 Added the number 25 and 21 more terms - V. Raman, Aug 28 2012 STATUS approved

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Last modified November 30 06:55 EST 2023. Contains 367454 sequences. (Running on oeis4.)