A089986 Numbers n such that 4n + 7 is prime.

-1, 0, 1, 3, 4, 6, 9, 10, 13, 15, 16, 18, 19, 24, 25, 30, 31, 33, 36, 39, 40, 43, 46, 48, 51, 54, 55, 58, 61, 64, 66, 69, 75, 76, 81, 85, 88, 90, 93, 94, 103, 106, 108, 109, 114, 115, 118, 120, 121, 123, 124, 129, 135, 139, 141, 145, 148, 150, 153, 156, 159, 160, 163, 169

Offset: 1

Author

Giovanni Teofilatto, Jan 13 2004

Keywords

• sign

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.

Crossrefs

Cf. A005099 ((( Primes = -1 mod 4 ) + 1)/4), A005098 (4n+1 is prime), A095278 (4n+3 is prime), A111215 (4n+5 is prime).

Programs

Magma

[ n: n in [-1..170] | IsPrime(4*n+7) ];

Maple

A089986:=n->`if`(isprime(4*n+7), n, NULL): seq(A089986(n), n=-1..200); # Wesley Ivan Hurt, Sep 18 2014

Mathematica

Select[Range[-1, 200], PrimeQ[4 # + 7] &] (* Wesley Ivan Hurt, Sep 18 2014 *)

PARI

is(n)=isprime(4*n+7) \\ Charles R Greathouse IV, Feb 20 2017

Formula

a(n) = A005099(n) - 2 = A095278(n) - 1.

Extensions

Edited and extended by Klaus Brockhaus, Dec 22 2008