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A121765 Numbers n such that 6*n-1 is composite while 6*n+1 is prime. 8
6, 11, 13, 16, 21, 26, 27, 35, 37, 46, 51, 55, 56, 61, 62, 63, 66, 68, 73, 76, 81, 83, 90, 91, 96, 101, 102, 105, 112, 115, 118, 121, 122, 123, 125, 126, 128, 131, 142, 146, 151, 153, 156, 161, 165, 166, 168, 173, 178, 181, 186, 187, 188, 195, 200, 202, 206, 208, 216 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Entries in A046953 which are not in A060461 or equivalently, entries in A024899 which are not in A002822.

LINKS

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

MATHEMATICA

Select[Range[250], ! PrimeQ[6# - 1] && PrimeQ[6# + 1] &] (* Ray Chandler, Aug 22 2006 *)

PROG

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

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

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

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

CROSSREFS

Cf. A121764.

Sequence in context: A175021 A315367 A046953 * A315368 A315369 A102974

Adjacent sequences:  A121762 A121763 A121764 * A121766 A121767 A121768

KEYWORD

nonn

AUTHOR

Lekraj Beedassy, Aug 20 2006

EXTENSIONS

Extended by Ray Chandler, Aug 22 2006

STATUS

approved

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Last modified May 25 10:01 EDT 2020. Contains 334592 sequences. (Running on oeis4.)