A090658 Numbers n such that n-1 is a prime of the form 4k+3.

4, 8, 12, 20, 24, 32, 44, 48, 60, 68, 72, 80, 84, 104, 108, 128, 132, 140, 152, 164, 168, 180, 192, 200, 212, 224, 228, 240, 252, 264, 272, 284, 308, 312, 332, 348, 360, 368, 380, 384, 420, 432, 440, 444, 464, 468, 480, 488, 492, 500, 504, 524, 548, 564, 572

Offset: 1

Author

Giovanni Teofilatto, Dec 14 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

• Vincenzo Librandi, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A002145, A087915, A089193, A089257.

Programs

Mathematica

okQ[n_]:=Module[{x=n-1},PrimeQ[x]&&IntegerQ[(x-3)/4]];Select[Range[1,1000,1],okQ] (* Vincenzo Librandi, Dec 13 2011 *)
Select[4*Range[0,200]+3,PrimeQ]+1 (* Harvey P. Dale, Sep 25 2017 *)

Formula

a(n) = A087915(n)+A089257(n), A089193(n)+A089257(n)-5.

Extensions

Corrected and extended by T. D. Noe, Oct 25 2006