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A175731 Semiprimes m such that either 2m-1 or 2m+1 is prime, but not both. 0
4, 10, 14, 22, 26, 33, 34, 35, 39, 49, 55, 57, 65, 74, 82, 86, 87, 91, 95, 106, 111, 115, 119, 121, 129, 134, 142, 146, 155, 158, 159, 166, 169, 177, 183, 187, 194, 201, 205, 209, 215, 217, 219, 221, 249, 254, 262, 274, 278, 289, 299, 301, 303, 323, 326, 327, 329, 339, 341 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
a(1)=4 because 2*4-1=7=prime and 2*4+1=9=nonprime.
PROG
(PARI) isok(m) = (bigomega(m)==2) && bitxor(isprime(2*m-1), isprime(2*m+1)); \\ Michel Marcus, Feb 20 2023
CROSSREFS
Intersection of A001358 and A174047.
Sequence in context: A161366 A310424 A176551 * A242486 A060031 A112825
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected (15 removed) by R. J. Mathar, Aug 25 2010. Also corrected by D. S. McNeil.
STATUS
approved

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Last modified April 19 07:38 EDT 2024. Contains 371782 sequences. (Running on oeis4.)