A272902 Numbers n such that 6n - 5 is not prime.

1, 5, 9, 10, 15, 16, 20, 21, 23, 25, 29, 30, 32, 35, 37, 40, 42, 43, 44, 45, 49, 50, 51, 54, 55, 58, 60, 61, 65, 66, 68, 70, 72, 75, 76, 79, 80, 81, 83, 85, 86, 87, 89, 90, 93, 94, 95, 98, 99

Offset

1,2

Links

Table of n, a(n) for n=1..49.

Formula

a(n) ~ n. - Charles R Greathouse IV, May 09 2016

Example

a(2) = 5 because 6 * 5 - 5 = 25 that is composite.

Mathematica

Select[Range[100], Not[PrimeQ[6# - 5]] &] (* Alonso del Arte, May 09 2016 *)

Prog

(PARI) is(n)=!isprime(6*n-5) \\ Charles R Greathouse IV, May 09 2016

Crossrefs

Sequence in context: A140509 A314580 A314581 * A235033 A327593 A282757

Adjacent sequences: A272899 A272900 A272901 * A272903 A272904 A272905

Keyword

nonn,easy

Author

Carlos Valencia Alonso, May 09 2016

Status

approved