A093290 If S*2^k - 3 and S*2^k + 3 are primes for k=0 to 2, then a(n) = S/10.

1, 28, 56, 1204, 22715, 38857, 63812, 68684, 115318, 126560, 139958, 148274, 169043, 196945, 204232, 219065, 242578, 245371, 316288, 364672, 369985, 379435, 442316, 484274, 579068, 601447, 606242, 650342, 825797, 851179, 943915, 952700

Offset

1,2

Links

Table of n, a(n) for n=1..32.

Example

a(3) = 56: S = 560.
560*2^0-3 = 557; 560*2^0+3 = 563; 557 and 563 are primes.
560*2^1-3 = 1117; 560*2^1+3 = 1123; 1117 and 1123 are primes.
560*2^2-3 = 2237; 560*2^2+3 = 2243; 2237 and 2243 are primes.

Mathematica

Select[ Range[10, 989650, 10], PrimeQ[ # - 3] && PrimeQ[ # + 3] && PrimeQ[2# - 3] && PrimeQ[2# + 3] && PrimeQ[4# - 3] && PrimeQ[4# + 3] &]/10 (* Robert G. Wilson v *)

Crossrefs

Sequence in context: A270297 A068576 A272185 * A181455 A042554 A042552

Adjacent sequences: A093287 A093288 A093289 * A093291 A093292 A093293

Keyword

nonn

Author

Ray G. Opao, May 11 2004

Extensions

More terms from Robert G. Wilson v, May 13 2004

Status

approved