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A058501 Primes p such that largest odd factor of p-1 is not a prime (i.e., is composite or 1). 1
2, 3, 5, 17, 19, 31, 37, 43, 61, 67, 71, 73, 79, 101, 103, 109, 127, 131, 139, 151, 157, 163, 181, 191, 197, 199, 211, 223, 229, 239, 241, 251, 257, 271, 277, 281, 283, 307, 311, 313, 331, 337, 349, 367, 373, 379, 397, 401, 409, 419, 421, 431, 433, 439, 443 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

FORMULA

Nonprimes in A057023.

EXAMPLE

127 is here because 127 - 1 = 126 = 2*63 and 63 is not a prime. 2 is here because 2 - 1 = 1 = 1*2^0 and 1 is not a prime.

MATHEMATICA

lofQ[n_]:=Module[{c=Select[Divisors[n-1], OddQ][[-1]]}, !PrimeQ[c]]; Select[ Prime[ Range[100]], lofQ] (* Harvey P. Dale, Jul 24 2021 *)

CROSSREFS

Cf. A057023, A006093.

Sequence in context: A129673 A215372 A290043 * A215356 A249410 A119405

Adjacent sequences:  A058498 A058499 A058500 * A058502 A058503 A058504

KEYWORD

nonn

AUTHOR

Labos Elemer, Dec 20 2000

STATUS

approved

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Last modified December 3 21:17 EST 2021. Contains 349468 sequences. (Running on oeis4.)