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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
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
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: A162821 A313360 A313361 * A112776 A313362 A120063
KEYWORD
nonn,easy
AUTHOR
Anton Joha, Jan 26 2001
EXTENSIONS
More terms from Henry Bottomley, Jan 29 2001
STATUS
approved