

A158573


Numbers k such that 30*k + 7 is prime.


9



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, 37, 41, 43, 44, 48, 52, 53, 54, 55, 58, 59, 62, 66, 67, 71, 76, 78, 79, 81, 82, 85, 87, 88, 89, 90, 92, 93, 95, 96, 97, 101, 102, 106, 107, 110, 115, 117, 118, 120, 121, 123, 124, 128
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OFFSET

1,3


COMMENTS

Encoded primes with LSD 7 and (SOD1)/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.


LINKS

Table of n, a(n) for n=1..68.


FORMULA

a(n) = (A132231(n)  7)/30 = floor(A132231(n)/30).  Ray Chandler, Apr 07 2009
a(n) ~ (4/15) n log n.  Charles R Greathouse IV, Mar 07 2016


EXAMPLE

Example: 3877, with LSD 7 and (SOD1)/3 = 23 (integer); Then 3877/30 = 129.233, or 129, which is in the sequence, and thus 3877 is prime.


MATHEMATICA

Select[Range[0, 200], PrimeQ[30#+7]&] (* Harvey P. Dale, Jul 20 2018 *)


PROG

(PARI) is(n)=isprime(30*n+7) \\ Charles R Greathouse IV, Mar 07 2016


CROSSREFS

Cf. A111175, A158614, A158648, A158746, A158791, A158806, A158850.
Sequence in context: A037472 A096304 A119955 * A194398 A047603 A047362
Adjacent sequences: A158570 A158571 A158572 * A158574 A158575 A158576


KEYWORD

nonn


AUTHOR

Ki Punches, Mar 21 2009


EXTENSIONS

Edited by Ray Chandler, Apr 07 2009


STATUS

approved



