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URL: https://oeis.org/A115396

⇱ A115396 - OEIS


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A115396
Smallest prime p such that p +- 2*n are semiprimes.
0
23, 29, 71, 17, 59, 37, 71, 41, 67, 29, 43, 109, 59, 37, 173, 53, 43, 151, 47, 79, 127, 79, 97, 73, 71, 67, 79, 89, 83, 109, 71, 79, 151, 101, 139, 97, 109, 101, 127, 89, 103, 239, 101, 97, 211, 113, 109, 151, 107, 109, 151, 113, 131, 157, 149, 137, 139, 131
OFFSET
1,1
EXAMPLE
a(100)=251 because 251-2*100=51=7*17 (semiprime), 251+2*100=451=11*41 (semiprime) [corrected by Sean A. Irvine, Nov 18 2025].
MATHEMATICA
sp[n_]:=Module[{p=NextPrime[2n]}, While[PrimeOmega[p+2n]!=2||PrimeOmega[p-2n]!=2, p=NextPrime[p]]; p]; Array[sp, 60] (* Harvey P. Dale, Nov 19 2025 *)
CROSSREFS
Sequence in context: A092518 A355983 A110584 * A180538 A227217 A229176
KEYWORD
nonn
AUTHOR
Zak Seidov, Mar 08 2006
EXTENSIONS
Corrected by Sean A. Irvine and Harvey P. Dale, Nov 18 2025
STATUS
approved