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 A336719 Largest odd prime p for which the order of 2 mod p is at most n. 3
 3, 7, 7, 31, 31, 127, 127, 127, 127, 127, 127, 8191, 8191, 8191, 8191, 131071, 131071, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 524287, 2147483647, 2147483647, 2147483647, 2147483647, 2147483647, 2147483647 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS a(1) is undefined. Changing "at most n" to "equal to n" in the definition gives A097406. The first term that is not a Mersenne prime (A000668) is 4432676798593. For a version without duplicates, see A336720. For a list of all n where a(n) increases, see A336721. LINKS Jeppe Stig Nielsen, Table of n, a(n) for n = 2..251 PROG (PARI) re=0; for(n=2, +oo, p=vecmax(factor(2^n-1)[, 1]); p>re&&re=p; print1(re, ", ")) CROSSREFS Cf. A000668, A005420, A014664, A097406, A336720, A336721. Sequence in context: A077629 A184467 A004794 * A272981 A086839 A316258 Adjacent sequences:  A336716 A336717 A336718 * A336720 A336721 A336722 KEYWORD nonn AUTHOR Jeppe Stig Nielsen, Aug 01 2020 STATUS approved

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Last modified July 29 06:21 EDT 2021. Contains 346340 sequences. (Running on oeis4.)