A121763 - OEIS

%I #15 Sep 08 2022 08:45:27

%S 4,8,9,14,15,19,22,28,29,39,42,43,44,49,53,59,60,64,65,67,74,75,78,80,

%T 82,84,85,93,94,98,99,108,109,113,114,117,120,124,127,129,133,140,144,

%U 148,152,155,157,158,159,162,163,164,169,183,184,185,194,197,198,199

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

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

%H G. C. Greubel, <a href="/A121763/b121763.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[200], PrimeQ[6# -1] && !PrimeQ[6# +1] &] (* _Ray Chandler_, Aug 22 2006 *)

%o (PARI) for(n=1, 250, if(isprime(6*n-1) && !isprime(6*n+1), print1(n", "))) \\ _G. C. Greubel_, Feb 20 2019

%o (Magma) [n: n in [1..250] | IsPrime(6*n-1) and not IsPrime(6*n+1)]; // _G. C. Greubel_, Feb 20 2019

%o (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

%o (GAP) Filtered([1..250], k-> IsPrime(6*k-1) and not IsPrime(6*k+1)) # _G. C. Greubel_, Feb 20 2019

%Y Cf. A121762, A121765.

%K nonn

%O 1,1

%A _Lekraj Beedassy_, Aug 20 2006

%E Extended by _Ray Chandler_, Aug 22 2006