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A023228 Numbers k such that k and 8*k + 1 are both prime. 9
2, 5, 11, 17, 29, 71, 101, 107, 131, 137, 149, 179, 239, 269, 347, 401, 431, 449, 479, 491, 509, 557, 599, 617, 659, 677, 761, 809, 821, 857, 929, 941, 947, 977, 1151, 1187, 1229, 1289, 1307, 1361, 1367, 1409, 1487, 1559, 1571, 1601, 1619, 1667, 1697, 1811, 1871 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Solutions of the equation (8*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

MATHEMATICA

Select[Prime[Range[2000]], PrimeQ[8# + 1]&] (* Vincenzo Librandi, Feb 02 2014 *)

PROG

(MAGMA) [ p: p in PrimesUpTo(1900) | IsPrime(8*p+1) ]; // Klaus Brockhaus, Dec 21 2008

CROSSREFS

Cf. A007519 (primes of form 8n+1), A005123 ((( primes == 1 mod 8 ) - 1)/8). - Klaus Brockhaus, Dec 21 2008

Sequence in context: A228353 A055499 A014424 * A027429 A336376 A059987

Adjacent sequences:  A023225 A023226 A023227 * A023229 A023230 A023231

KEYWORD

nonn,easy

AUTHOR

David W. Wilson

STATUS

approved

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Last modified July 26 22:49 EDT 2021. Contains 346300 sequences. (Running on oeis4.)