A111175 Numbers n such that 30*n + 1 is prime.

1, 2, 5, 6, 7, 8, 9, 11, 14, 18, 19, 20, 21, 22, 23, 25, 27, 33, 34, 35, 39, 40, 41, 43, 44, 46, 49, 51, 54, 58, 60, 61, 62, 65, 67, 71, 72, 74, 75, 76, 77, 78, 79, 84, 85, 89, 91, 93, 95, 99, 100, 102, 104, 106, 109, 110, 111, 112, 113, 117, 118, 119, 121, 123, 131, 134, 135

Offset

1,2

Comments

Encoded primes with LSD 1 and (SOD-1)/3 integer, (LSD, least significant digit; SOD, sum of digits). Divide any such number by 30, if the whole number portion of the quotient is in the sequence, the number is prime. Example: 2671, with LSD 1 and (SOD-1)/3 = 2 (integer); Then 2671/30 = 89.033, or 89, which is in the sequence, and thus 2671 is prime. - Ki Punches, Mar 18 2009

Links

Table of n, a(n) for n=1..67.

Formula

a(n) = (A132230(n) - 1)/30 = Floor[A132230(n)/30]. - Chandler

Example

If n=99 then 30*n + 1 = 2971 (prime).

Prog

(PARI) is(n)=isprime(30*n+1) \\ Charles R Greathouse IV, Feb 17 2017

Crossrefs

Cf. A158573, A158614, A158648, A158746, A158791, A158806, A158850.

Sequence in context: A202114 A228090 A287440 * A047326 A039044 A212441

Adjacent sequences: A111172 A111173 A111174 * A111176 A111177 A111178

Keyword

nonn

Author

Parthasarathy Nambi, Oct 21 2005

Extensions

Extended by Ray Chandler, Apr 07 2009

Status

approved