A201734 Numbers n such that 90*n + 47 is prime.

0, 1, 2, 3, 6, 7, 9, 10, 13, 14, 16, 18, 20, 22, 24, 25, 27, 29, 31, 32, 38, 39, 43, 44, 49, 50, 51, 53, 56, 63, 64, 65, 66, 69, 77, 80, 83, 84, 87, 90, 91, 95, 98, 101, 102, 105, 106, 107, 108, 109, 111, 116, 118, 120, 121, 122, 123, 129, 132, 134, 135, 137

Offset: 1

Author

J. W. Helkenberg, Dec 04 2011

Keywords

• nonn
• easy
• less

Comments

A reverse reading of A142313; all entries of A142313 have digital root 2 and last digit 7.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A181732, A198382, A195993, A196000, A196007.

Programs

Magma

[n: n in [0..200] | IsPrime(90*n+47)]; // Vincenzo Librandi, Dec 11 2011

Maple

for n from 0 to 240 do
    p := 90*n+47 ;
    if isprime(p) then
        printf("%d,",n) ;
    end if;
end do: # R. J. Mathar, Dec 05 2011

Mathematica

Select[Range[0,400],PrimeQ[90 #+47]&] (* Vincenzo Librandi, Dec 11 2011 *)

PARI

is(n)=isprime(90*n+47) \\ Charles R Greathouse IV, Feb 17 2017

Formula

a(n) = (A142313(n)-47)/90.