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A059324 Numbers n such that 6n + 5 is composite. 6
5, 10, 12, 15, 19, 20, 23, 25, 26, 30, 33, 34, 35, 36, 40, 45, 47, 49, 50, 53, 54, 55, 56, 60, 61, 62, 65, 67, 68, 70, 72, 75, 78, 80, 82, 85, 87, 88, 89, 90, 91, 95, 96, 100, 101, 103, 104, 105, 110, 111, 114, 115, 117, 118, 120, 121, 122, 124, 125, 127, 129, 130 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: There exists no pair of primes (p, q > p^2) such that q - p^2 = 6*n - 4 (see A138479). - Philippe LALLOUET (philip.lallouet(AT)orange.fr), Mar 20 2008

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..5000

FORMULA

a(n) = A046953(n-1) - 1.

EXAMPLE

a(3) = 12 because 6*12 + 5 = 77 is composite.

MATHEMATICA

Select[Range[200], !PrimeQ[6#+5]&]  (* Harvey P. Dale, Mar 13 2011 *)

PROG

(PARI) isok(n) = ! isprime(6*n+5); \\ Michel Marcus, Jan 06 2017

CROSSREFS

Complement of A059325.

Cf. A138479.

Sequence in context: A050680 A293726 A162821 * A112776 A120063 A285683

Adjacent sequences:  A059321 A059322 A059323 * A059325 A059326 A059327

KEYWORD

nonn,easy

AUTHOR

Anton Joha, Jan 26 2001

EXTENSIONS

More terms from Henry Bottomley, Jan 29 2001

STATUS

approved

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Last modified November 19 03:50 EST 2017. Contains 294912 sequences.