A089253 Numbers n such that 2n - 5 is a prime.

4, 5, 6, 8, 9, 11, 12, 14, 17, 18, 21, 23, 24, 26, 29, 32, 33, 36, 38, 39, 42, 44, 47, 51, 53, 54, 56, 57, 59, 66, 68, 71, 72, 77, 78, 81, 84, 86, 89, 92, 93, 98, 99, 101, 102, 108, 114, 116, 117, 119, 122, 123, 128, 131, 134, 137, 138, 141, 143, 144, 149, 156, 158, 159, 161

Offset: 1

Author

Giovanni Teofilatto, Dec 12 2003

Keywords

• easy
• nonn

References

• M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988
• Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta, UTET, CittaStudiEdizioni, Milano 1997

Links

• Shawn A. Broyles, Table of n, a(n) for n = 1..1000

Crossrefs

Numbers n such that 2n+k is prime: A005097 (k=1), A067076 (k=3), A089038 (k=5), A105760 (k=7), A155722 (k=9), A101448 (k=11), A153081 (k=13), A089559 (k=15), A173059 (k=17), A153143 (k=19).

Numbers n such that 2n-k is prime: A006254 (k=1), A098090 (k=3), this sequence (k=5), A089192 (k=7), A097069 (k=9), A097338 (k=11), A097363 (k=13), A097480 (k=15), A098605 (k=17), A097932 (k=19).

Programs

Mathematica

(Prime[Range[2,100]]+5)/2 (* Vladimir Joseph Stephan Orlovsky, Feb 08 2010 *)
Select[Range[2,200],PrimeQ[2#-5]&] (* Harvey P. Dale, Dec 29 2024 *)

PARI

a(n)=prime(n+1)\2+3 \\ Charles R Greathouse IV, Oct 30 2012

Formula

a(n) = A067076(n) + 4. - Giovanni Teofilatto, Dec 14 2003

Extensions

Corrected by Ralf Stephan, Mar 03 2004

Further correction from Jeremy Gardiner, Sep 11 2004