A083685 a(n) is the smallest prime of the form k*lcm(1..n) - 1.

2, 3, 5, 11, 59, 59, 419, 839, 5039, 5039, 55439, 55439, 1081079, 1081079, 1081079, 1441439, 24504479, 24504479, 232792559, 232792559, 232792559, 232792559, 5354228879, 5354228879, 53542288799, 53542288799, 1044074631599

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..500

Example

a(9) = 5039: lcm(1..9) = 2520; 2519 is not a prime but 2*2520 - 1 = 5039 is a prime.

Mathematica

spf[n_]:=Module[{c=LCM@@Range[n], k=1}, While[!PrimeQ[k*c-1], k++]; k*c-1]; Array[spf, 30] (* Harvey P. Dale, Jan 15 2022 *)

Prog

(PARI) a(n) = {my(lcmn = lcm(vector(n, k, k)), k = 1); while(!isprime(p = k*lcmn-1), k++); p; } \\ Michel Marcus, Mar 15 2018

Crossrefs

Cf. A070858.

Sequence in context: A000905 A065296 A114895 * A243755 A242334 A087524

Adjacent sequences: A083682 A083683 A083684 * A083686 A083687 A083688

Keyword

nonn

Author

Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 15 2003

Extensions

Corrected and extended by Vladeta Jovovic, Jun 16 2003

Status

approved