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A165810 Primes p such that 18*p+1 is also a prime. 2
2, 7, 11, 17, 29, 41, 59, 71, 79, 97, 127, 137, 139, 149, 151, 181, 197, 199, 241, 251, 277, 281, 307, 337, 347, 367, 379, 401, 431, 479, 491, 541, 569, 587, 659, 701, 709, 757, 797, 809, 821, 827, 829, 857, 877, 881, 947, 991, 1021, 1051, 1109, 1117, 1129, 1151, 1229 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Solutions of the equation (18*n+1)' + n' = 2, where n' is the arithmetic derivative of n. - Paolo P. Lava, Oct 31 2012

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = (A165811(n)-1)/18.

EXAMPLE

For p=2, 18*p+1=37. For p=7, 18*p+1=127. For p=11, 18*p+1=199.

MATHEMATICA

Select[Prime[Range[1000]], PrimeQ[18#+1]&]  (* Harvey P. Dale, Mar 06 2011 *)

CROSSREFS

Cf. A111094, A153400, A165811.

Sequence in context: A124854 A240878 A109953 * A109417 A045372 A273600

Adjacent sequences:  A165807 A165808 A165809 * A165811 A165812 A165813

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Sep 28 2009

EXTENSIONS

Extended by R. J. Mathar, Oct 16 2009

STATUS

approved

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Last modified February 26 18:29 EST 2020. Contains 332293 sequences. (Running on oeis4.)