A120226 - OEIS

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A120226

Numbers k such that 4+k and 4*k+1 are prime.

1, 3, 7, 9, 13, 15, 25, 27, 37, 39, 43, 49, 57, 67, 69, 79, 93, 97, 99, 105, 127, 135, 153, 163, 169, 175, 177, 189, 193, 207, 219, 235, 253, 265, 267, 273, 277, 279, 303, 307, 309, 343, 345, 363, 405, 417, 427, 435, 475, 483, 487, 499, 517, 553, 559, 567, 573

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OFFSET

1,2

COMMENTS

Except for 3, no terms == 3 or 5 (mod 7). - Robert Israel, Jul 26 2019

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

select(t -> isprime(t+4) and isprime(4*t+1), [seq(i, i=1..1000, 2)]); # Robert Israel, Jul 26 2019

MATHEMATICA

Select[Range[600], AllTrue[{4+#, 4#+1}, PrimeQ]&] (* Harvey P. Dale, Nov 14 2022 *)

CROSSREFS

Cf. A092945, A106057, A085063, A120223, A120224, A120225, A120227.

Sequence in context: A000959 A204085 A230076 * A137310 A118567 A118561

Adjacent sequences: A120223 A120224 A120225 * A120227 A120228 A120229

KEYWORD

nonn

AUTHOR

Zak Seidov, Jun 10 2006

STATUS

approved

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