A201819 Numbers n such that 90*n + 31 is prime.

0, 2, 6, 7, 8, 11, 13, 14, 15, 16, 19, 20, 22, 25, 26, 28, 30, 33, 35, 36, 37, 39, 40, 47, 49, 51, 53, 60, 61, 63, 64, 65, 68, 71, 74, 75, 76, 77, 81, 82, 84, 85, 88, 91, 92, 95, 97, 99, 104, 107, 110, 112, 118, 120, 128, 130, 131, 138, 139, 141, 146, 149

Offset: 1

Author

J. W. Helkenberg, Dec 05 2011

Keywords

• nonn
• easy

Comments

This sequence was generated by adding 14 Fibonacci-like sequences. Looking at the format 90n+31 modulo 9 and modulo 10 we see that all entries of A142328 have digital root 4 and last digit 1. (Reverting the process is an application of the Chinese remainder theorem.)

Links

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

Crossrefs

Cf. A181732, A198382, A195993, A196000, A196007, A201739, A201734, A201804, A201816, A201818.

Programs

Magma

[n: n in [0..200] | IsPrime(90*n+31)] // Vincenzo Librandi, Dec 11 2011

Mathematica

Select[Range[0, 200], PrimeQ[90 # + 31] &] (* T. D. Noe, Dec 06 2011 *)

PARI

is(n)=isprime(90*n+31) \\ Charles R Greathouse IV, Feb 20 2017