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A083733 Pseudoprimes to bases 2 and 7. 3
561, 1105, 2465, 3277, 8321, 10585, 18721, 29341, 46657, 62745, 75361, 104653, 115921, 162401, 219781, 226801, 252601, 278545, 294409, 314821, 334153, 340561, 399001, 410041, 449065, 488881, 512461, 530881, 534061, 552721, 574561, 587861 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..15498 (terms 1..138 from R. J. Mathar)
FORMULA
a(n) = n-th positive integer k(>1) such that 2^(k-1) = 1 (mod k) and 7^(k-1) = 1 (mod k).
EXAMPLE
a(1)=561 since it is the first positive integer k(>1) which satisfies 2^(k-1) = 1 (mod k) and 7^(k-1) = 1 (mod k).
PROG
(PARI) is(n)=!isprime(n)&&Mod(2, n)^(n-1)==1&&Mod(7, n)^(n-1)==1 \\ Charles R Greathouse IV, Apr 12 2012
CROSSREFS
Intersection of A005938 and A001567. - R. J. Mathar, Apr 05 2011
Sequence in context: A300629 A135720 A263403 * A339869 A214428 A262043
KEYWORD
nonn
AUTHOR
Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), May 05 2003
STATUS
approved

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)