A111175 - OEIS

%I #10 Feb 17 2017 14:55:36

%S 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,

%T 46,49,51,54,58,60,61,62,65,67,71,72,74,75,76,77,78,79,84,85,89,91,93,

%U 95,99,100,102,104,106,109,110,111,112,113,117,118,119,121,123,131,134,135

%N Numbers n such that 30*n + 1 is prime.

%C 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

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

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

%o (PARI) is(n)=isprime(30*n+1) \\ _Charles R Greathouse IV_, Feb 17 2017

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

%K nonn

%O 1,2

%A _Parthasarathy Nambi_, Oct 21 2005

%E Extended by _Ray Chandler_, Apr 07 2009