A228121 Numbers n such that 3n - 4 is prime.

2, 3, 5, 7, 9, 11, 15, 17, 19, 21, 25, 29, 31, 35, 37, 39, 45, 47, 51, 57, 59, 61, 65, 67, 77, 79, 81, 85, 87, 89, 91, 95, 99, 105, 107, 117, 119, 121, 129, 131, 135, 141, 145, 149, 151, 155, 157, 161, 165, 169, 171, 175, 187, 189, 191, 197, 199, 201, 207, 215, 217, 219, 221, 227, 229

Offset: 1

Author

Irina Gerasimova, Aug 11 2013

Keywords

• nonn
• less
• easy

Comments

Primes in a(n): 2, 3, 5, 7, 11, 17, 19, 29, 31, 37, 47, 59, 61, 67, 79, 89, 107, 131, 149, 151, 157, 191, 197, 199, 227, 229, 241, 271, 277, 281,...

Examples

			For n = 15, 3*15 - 4 = 41 is prime.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A008585, A153183, A228358.

Programs

Mathematica

Select[Range[300],PrimeQ[3#-4]&] (* Harvey P. Dale, Mar 30 2020 *)

PARI

is(n)=isprime(3*n-4) \\ Charles R Greathouse IV, Mar 17 2014

Formula

a(n) = A024893(n) + 2. - Michael B. Porter, Aug 11 2013