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A046954 Numbers n such that 6n+1 is nonprime. 11
0, 4, 8, 9, 14, 15, 19, 20, 22, 24, 28, 29, 31, 34, 36, 39, 41, 42, 43, 44, 48, 49, 50, 53, 54, 57, 59, 60, 64, 65, 67, 69, 71, 74, 75, 78, 79, 80, 82, 84, 85, 86, 88, 89, 92, 93, 94, 97, 98, 99, 104, 106, 108, 109, 111, 113, 114, 116, 117, 119, 120, 124, 127, 129, 130, 132, 133, 134, 136, 139, 140 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A046954 = A171696 U A121763; A121765 U A171696 = A046953; A121763 U A121765 = A067611 where A067611 U A002822 U A171696 = A001477. - Juri-Stepan Gerasimov, Feb 13 2010, Feb 15 2010

Numbers (except 0) can be written as 6xy ±(x+y) for x>0, y>0. - Ron R Spencer, Aug 01 2016

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

EXAMPLE

a(2)=8 because 6*8+1=49 which is composite.

MATHEMATICA

a = Flatten[Table[If[PrimeQ[6*n + 1] == False, n, {}], {n, 0, 50}]] (* Roger L. Bagula, May 17 2007 *)

Select[Range[0, 200], !PrimeQ[6 # + 1] &] (* Vincenzo Librandi, Sep 27 2013 *)

PROG

(MAGMA) /* see example triangle */ [[(2*n*k+n+k)/3: k in [1..n]]: n in [1..15]]; // Vincenzo Librandi, Sep 27 2013

(Haskell)

a046954 n = a046954_list !! (n-1)

a046954_list = map (`div` 6) $ filter ((== 0) . a010051' . (+ 1)) [0, 6..]

-- Reinhard Zumkeller, Jul 13 2014

(PARI) is(n)=!isprime(6*n+1) \\ Charles R Greathouse IV, Aug 01 2016

CROSSREFS

Cf. A047845 (2n+1), A045751 (4n+1), A127260 (8n+1).

Cf. A046953, A008588, A016921, subsequence of A067611.

Sequence in context: A163408 A060299 A120512 * A112775 A107747 A121763

Adjacent sequences:  A046951 A046952 A046953 * A046955 A046956 A046957

KEYWORD

nonn

AUTHOR

Felice Russo

EXTENSIONS

Edited by N. J. A. Sloane, Aug 08 2008 at the suggestion of R. J. Mathar

Corrected by Juri-Stepan Gerasimov, Feb 13 2010, Feb 15 2010

Corrected by Vincenzo Librandi, Sep 27 2013

STATUS

approved

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Last modified November 18 10:38 EST 2017. Contains 294887 sequences.