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A182030 Least odd number k such that 3*k*2^n-1 and 3*k*2^n+1 are twin primes. 1
1, 1, 3, 5, 27, 1, 3, 19, 15, 5, 33, 55, 123, 15, 115, 39, 127, 1, 23, 149, 27, 11, 393, 81, 255, 125, 27, 129, 15, 115, 227, 195, 125, 89, 247, 71, 143, 1031, 55, 89, 85, 365, 3, 49, 283, 135, 497, 59, 647, 309, 375, 399, 667, 111, 173, 355, 195, 219, 43, 49 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

54% of a(n) for n=1 to 1755 are < 0.1*n^2.

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..1755

MATHEMATICA

lon[n_]:=Module[{k=1, n2=3*2^n}, While[!PrimeQ[k*n2-1]||!PrimeQ[k*n2+1], k= k+2]; k]; Array[lon, 60] (* Harvey P. Dale, Nov 27 2015 *)

CROSSREFS

Cf. A210651.

Sequence in context: A154143 A101611 A268409 * A282141 A318321 A279510

Adjacent sequences:  A182027 A182028 A182029 * A182031 A182032 A182033

KEYWORD

nonn

AUTHOR

Pierre CAMI, Apr 07 2012

STATUS

approved

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Last modified October 16 19:00 EDT 2018. Contains 316271 sequences. (Running on oeis4.)