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A367231 Carmichael numbers k such that the multiplicative order of 2 modulo k is odd. 2
15841, 52633, 5049001, 68154001, 104852881, 238244041, 382536001, 3215031751, 3863326897, 7211236033, 8214723001, 15462960481, 22008493921, 23000028481, 29392867201, 31708772257, 41217865921, 53125756201, 60518537641, 74190097801, 77874636001, 83828294551, 103387371361 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
These Carmichael numbers seem to be relatively rare: among the 4279356 Carmichael numbers below 2^64 only 3097 are terms of this sequence.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (calculated using data from Claude Goutier)
MATHEMATICA
Select[2*Range[3*10^6] + 1, Mod[#, CarmichaelLambda[#]] == 1 && CompositeQ[#] && OddQ[MultiplicativeOrder[2, #]] &]
PROG
(PARI) is(n) = n > 1 && n % 2 && !isprime(n) && n % lcm(znstar(n)[2]) == 1 && znorder(Mod(2, n)) % 2;
CROSSREFS
Intersection of A002997 and A036259.
Subsequence of A367230.
Sequence in context: A216180 A112450 A063847 * A265669 A356866 A184612
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 11 2023
STATUS
approved

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Last modified June 19 18:58 EDT 2024. Contains 373507 sequences. (Running on oeis4.)