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A024912 Numbers n such that 10n + 1 is prime. 19
1, 3, 4, 6, 7, 10, 13, 15, 18, 19, 21, 24, 25, 27, 28, 31, 33, 40, 42, 43, 46, 49, 52, 54, 57, 60, 63, 64, 66, 69, 70, 75, 76, 81, 82, 88, 91, 94, 97, 99, 102, 103, 105, 106, 109, 115, 117, 118, 120, 123, 129, 130, 132, 136, 138, 145, 147, 148, 151, 153, 157, 160, 162 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Solutions of the equation (10*n+1)' = 1, where n' is the arithmetic derivative of n. [Paolo P. Lava, Nov 15 2012]

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = (A081759(n)+1)/2.

MATHEMATICA

Select[Range[170], PrimeQ[10# + 1] &] (* Ray Chandler, Dec 06 2006 *)

PROG

(MAGMA) [n: n in [1..1000] |IsPrime(10*n+1)] // Vincenzo Librandi, Nov 19 2010]

(PARI) is(n)=isprime(10*n+1) \\ Charles R Greathouse IV, Jul 02 2013

CROSSREFS

Cf. A030430, A049511, A081759.

Sequence in context: A317138 A032387 A026313 * A108588 A194095 A064404

Adjacent sequences:  A024909 A024910 A024911 * A024913 A024914 A024915

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified April 19 11:58 EDT 2021. Contains 343114 sequences. (Running on oeis4.)