OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
EXAMPLE
a(7)=11, since 2^11-11= 3*7*97 and 2^k-k is not divisible by 7 for 0<=k<11.
MATHEMATICA
b[n_] := Module[{k = 0}, While[! Divisible[2^k - k, n], k++]; k]; Array[b, 25] (* G. C. Greubel, Oct 11 2016 *)
PROG
(PARI) a(n) = {my(k = 0); while ((2^k-k) % n, k++); k; } \\ Michel Marcus, Aug 18 2013
(Magma)
S:=[0];
k:=1;
for n in [2..80] do
while not IsZero((2^k-k) mod n) do
k:=k+1;
end while;
Append(~S, k);
k:=1;
end for;
S; // Bruno Berselli, Aug 18 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
John L. Drost, Feb 16 2008
EXTENSIONS
Edited by N. J. A. Sloane, May 27 2010
STATUS
approved