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%I #12 Jul 20 2018 11:23:18
%S 0,1,2,3,4,5,9,10,11,12,13,15,16,18,19,20,24,25,26,29,30,31,32,33,36,
%T 37,41,43,44,48,52,53,54,55,58,59,62,66,67,71,76,78,79,81,82,85,87,88,
%U 89,90,92,93,95,96,97,101,102,106,107,110,115,117,118,120,121,123,124,128
%N Numbers k such that 30*k + 7 is prime.
%C Encoded primes with LSD 7 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.
%F a(n) = (A132231(n) - 7)/30 = floor(A132231(n)/30). - _Ray Chandler_, Apr 07 2009
%F a(n) ~ (4/15) n log n. - _Charles R Greathouse IV_, Mar 07 2016
%e Example: 3877, with LSD 7 and (SOD-1)/3 = 23 (integer); Then 3877/30 = 129.233, or 129, which is in the sequence, and thus 3877 is prime.
%t Select[Range[0,200],PrimeQ[30#+7]&] (* _Harvey P. Dale_, Jul 20 2018 *)
%o (PARI) is(n)=isprime(30*n+7) \\ _Charles R Greathouse IV_, Mar 07 2016
%Y Cf. A111175, A158614, A158648, A158746, A158791, A158806, A158850.
%K nonn
%O 1,3
%A _Ki Punches_, Mar 21 2009
%E Edited by _Ray Chandler_, Apr 07 2009
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