A243341 Least number k such that k^n - k^(n-1) - k^(n-2) - ... - k^2 - k - 1 is prime.

3, 3, 4, 3, 4, 4, 30, 4, 4, 15, 4, 27, 54, 10, 4, 3, 10, 11, 56, 35, 4, 35, 8, 34, 6, 24, 32, 17, 6, 4, 18, 3, 100, 191, 10, 63, 54, 40, 4, 129, 20, 14, 474, 16, 142, 330, 20, 36, 116, 4, 664, 161, 32, 19, 62, 7, 54, 366, 132, 71, 162, 5, 4, 3, 204, 60, 18, 30, 198, 155, 28, 274, 6

Offset

1,1

Comments

a(n) > 2 for all n.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..200

Example

1^1-1 = 0 is not prime. 2^1-1 = 1 is not prime. 3^1-1 = 2 is prime. Thus a(1) = 3.

Mathematica

lnk[n_]:=Module[{k=2}, While[!PrimeQ[k^n-Total[k^Range[0, n-1]]], k++]; k]; Array[lnk, 80] (* Harvey P. Dale, Aug 26 2016 *)

Prog

(PARI) a(n)=for(k=1, 10^3, if(ispseudoprime(k^n-sum(i=0, n-1, k^i))), return(k)))
n=1; while(n<100, print1(a(n), ", "); n+=1)

Crossrefs

Sequence in context: A167596 A216190 A267592 * A238856 A096139 A175928

Adjacent sequences: A243338 A243339 A243340 * A243342 A243343 A243344

Keyword

nonn

Author

Derek Orr, Jun 03 2014

Status

approved