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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

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.

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 (SOD-1)/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

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Last modified June 13 22:55 EDT 2021. Contains 345016 sequences. (Running on oeis4.)