OFFSET
1,2
COMMENTS
Less than 10 % of a(n)=0.
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..4560
EXAMPLE
n=2:2^(2*n)-2^1-1=13 prime but n-1=1=k so k not > n-1.
2^(2*n)-2^2-1=11 prime k=2 k>n-1 so a(2)=2.
MATHEMATICA
Table[k = n; While[k < 2*n && ! PrimeQ[4^n - 2^k - 1], k++]; If[k == 2*n, k = 0]; k, {n, 100}] (* T. D. Noe, May 02 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Apr 28 2012
STATUS
approved