This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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: A190755 A098849 A319059 * A177835 A075698 A165493 Adjacent sequences:  A217192 A217193 A217194 * A217196 A217197 A217198 KEYWORD nonn AUTHOR Antonio Roldán, Sep 27 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 20 14:06 EDT 2019. Contains 326152 sequences. (Running on oeis4.)