A124417 a(n) = least k such that 2^i*k+1 is prime for 1<=i<=n.

1, 1, 9, 765, 765, 8325, 8325, 7757430, 428547690, 102764221560, 694561346985, 108428872433310, 379041973928475, 34628781572140470, 34628781572140470

Offset

1,3

Links

Table of n, a(n) for n=1..15.

Mathematica

k = 1; Do[If[n < 3, inc = 1, If[n == 3, inc = 3, inc = 15]; ]; If[Mod[k, inc] > 0, k = k + inc - Mod[k, inc]]; While[Nand @@ PrimeQ[Table[2^j, {j, n}]*k + 1], k += inc]; Print[k], {n, 1, 15}] (* Ray Chandler, Nov 21 2006 *)

Crossrefs

Cf. A005097, A123998, A124041, A124412, A124413, A124414, A124415, A124416.

Sequence in context: A185274 A246122 A145183 * A265463 A159356 A246123

Adjacent sequences: A124414 A124415 A124416 * A124418 A124419 A124420

Keyword

nonn,more

Author

Artur Jasinski, Nov 02 2006

Extensions

Edited by Ray Chandler, Nov 21 2006

a(10) from Farideh Firoozbakht, Nov 25 2006

a(11)-a(15) from Giovanni Resta, Apr 24 2019

Status

approved