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A201822 Numbers k such that 90*k + 77 is prime. 12
1, 2, 3, 6, 8, 9, 10, 15, 17, 18, 19, 20, 24, 26, 29, 30, 32, 34, 37, 40, 41, 43, 45, 46, 48, 54, 58, 59, 60, 62, 65, 68, 69, 74, 75, 76, 79, 82, 83, 85, 86, 87, 89, 93, 94, 95, 97, 102, 104, 109, 111, 113, 114, 115, 117, 122, 128, 130, 131, 135, 138, 144 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Looking at the format 90k+77 modulo 9 and modulo 10 we see that all entries of A142329 have digital root 5 and last digit 7. (Reverting the process is an application of the Chinese remainder theorem.)

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (A142329(n) - 77)/90.

MATHEMATICA

Select[Range[0, 400], PrimeQ[90 #+77]&] (* Vincenzo Librandi, Dec 11 2011 *)

PROG

(MAGMA) [n: n in [0..200] | IsPrime(90*n+77)]; // Vincenzo Librandi, Dec 11 2011

(PARI) is(n)=isprime(90*n+77) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. A181732, A198382, A195993, A196000, A196007, A201739, A201734, A201804, A201816, A201817, A201818, A201820.

Sequence in context: A047286 A344156 A344166 * A093510 A202341 A013948

Adjacent sequences:  A201819 A201820 A201821 * A201823 A201824 A201825

KEYWORD

nonn,easy

AUTHOR

J. W. Helkenberg, Dec 05 2011

STATUS

approved

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Last modified July 24 23:25 EDT 2021. Contains 346273 sequences. (Running on oeis4.)