A182030 Least odd number k such that 3*k*2^n-1 and 3*k*2^n+1 are twin primes.

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

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 * A348509 A282141 A318321

Adjacent sequences: A182027 A182028 A182029 * A182031 A182032 A182033

Keyword

nonn

Author

Pierre CAMI, Apr 07 2012

Status

approved