login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A124417 a(n) = least k such that 2^i*k+1 is prime for 1<=i<=n. 8
1, 1, 9, 765, 765, 8325, 8325, 7757430, 428547690, 102764221560, 694561346985, 108428872433310, 379041973928475, 34628781572140470, 34628781572140470 (list; graph; refs; listen; history; text; internal format)
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,changed

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 1 14:52 EDT 2020. Contains 333163 sequences. (Running on oeis4.)