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A217195 Primes p such that p-2 is the greatest semiprime less than p. 2
17, 37, 41, 53, 67, 71, 79, 89, 97, 113, 131, 157, 163, 211, 223, 239, 251, 269, 293, 307, 311, 331, 337, 367, 373, 379, 397, 409, 419, 439, 449, 487, 491, 499, 521, 547, 593, 599, 613, 631, 673, 683, 691, 701, 709, 733, 739, 751, 757, 769, 773, 787, 809 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This is a subsequence of A063638.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

EXAMPLE

487 is prime, 486 = 2*3^5 is not semiprime and 485 = 5*97 is semiprime.

MATHEMATICA

SemiPrimeQ[n_Integer] := If[Abs[n] < 2, False, (2 == Plus @@ Transpose[FactorInteger[Abs[n]]][[2]])]; Select[Prime[Range[200]], ! SemiPrimeQ[# - 1] && SemiPrimeQ[# - 2] &] (* T. D. Noe, Sep 27 2012 *)

PROG

(PARI) forprime(p=3, 9999, bigomega(p-2)==2 && bigomega(p-1)!=2 & print1(p", "))

CROSSREFS

Sequence in context: A116112 A190755 A098849 * A177835 A075698 A165493

Adjacent sequences:  A217192 A217193 A217194 * A217196 A217197 A217198

KEYWORD

nonn

AUTHOR

Antonio Roldán, Sep 27 2012

STATUS

approved

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Last modified January 21 13:52 EST 2018. Contains 297994 sequences.