A121763 Numbers n such that 6*n-1 is prime while 6*n+1 is composite.

4, 8, 9, 14, 15, 19, 22, 28, 29, 39, 42, 43, 44, 49, 53, 59, 60, 64, 65, 67, 74, 75, 78, 80, 82, 84, 85, 93, 94, 98, 99, 108, 109, 113, 114, 117, 120, 124, 127, 129, 133, 140, 144, 148, 152, 155, 157, 158, 159, 162, 163, 164, 169, 183, 184, 185, 194, 197, 198, 199

Offset: 1

Author

Lekraj Beedassy, Aug 20 2006

Keywords

• nonn

Comments

Entries of A024898 which are not in A002822 or equivalently, entries of A046954 which are not in A060461.

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A121762, A121765.

Programs

GAP

Filtered([1..250], k-> IsPrime(6*k-1) and not IsPrime(6*k+1)); # G. C. Greubel, Feb 20 2019

Magma

[n: n in [1..250] | IsPrime(6*n-1) and not IsPrime(6*n+1)]; // G. C. Greubel, Feb 20 2019

Mathematica

Select[Range[200], PrimeQ[6# -1] && !PrimeQ[6# +1] &] (* Ray Chandler, Aug 22 2006 *)

PARI

for(n=1, 250, if(isprime(6*n-1) && !isprime(6*n+1), print1(n", "))) \\ G. C. Greubel, Feb 20 2019

Sage

[n for n in (1..250) if is_prime(6*n-1) and not is_prime(6*n+1)] # G. C. Greubel, Feb 20 2019

Extensions

Extended by Ray Chandler, Aug 22 2006