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 A086249 Number of base-2 Fermat pseudoprimes x that have ord(2,x) = n. 4
 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 3, 1, 2, 1, 1, 0, 12, 4, 3, 0, 1, 1, 1, 1, 12, 1, 1, 4, 5, 1, 9, 4, 10, 8, 3, 4, 25, 0, 10, 11, 11, 4, 1, 4, 15, 4, 22, 1, 57, 0, 1, 4, 10, 1, 24, 1, 11, 1, 41, 4, 86, 4, 10, 25, 11, 0, 21, 4, 7, 4, 10, 1, 52, 1, 7, 10, 22, 0, 26, 11, 56, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,22 COMMENTS A base-2 Fermat pseudoprime is a composite number x such that 2^x == 2 (mod x). For such an x, ord(2,x) is the smallest positive integer m such that 2^m == 1 (mod x). For a number x to have order n, it must be a factor of 2^n-1 and not be a factor of 2^r-1 for r1 && (d-1)%n==0 && !ispseudoprime(d) && znorder(Mod(2, d), n)==n, r++) ); r } /* Max Alekseyev, Jan 07 2015 */ CROSSREFS Cf. A001567 (base-2 pseudoprimes), A086250. Sequence in context: A139569 A201590 A235358 * A176784 A176511 A243977 Adjacent sequences:  A086246 A086247 A086248 * A086250 A086251 A086252 KEYWORD hard,nonn AUTHOR T. D. Noe, Jul 14 2003 STATUS approved

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Last modified May 18 22:37 EDT 2022. Contains 353826 sequences. (Running on oeis4.)