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%I #39 Aug 03 2014 14:01:33
%S 1,1,1,0,1,0,0,0,1,0,1,0,1,0,0,0,2,0,1,0,0,0,0,0,1,0,1,0,1,0,0,0,3,0,
%T 0,0,1,0,0,0,2,0,3,0,0,0,0,0,0,0,0,0,1,0,0,0,3,0,1,0,1,0,0,0,5,0,1,0,
%U 0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0
%N Number of numbers k with 0 <= k < n such that 2^k + 1 is multiple of n.
%C a(A014657(n)) > 0; for n > 1: a(A014661(n)) = 0.
%H Reinhard Zumkeller, <a href="/A195470/b195470.txt">Table of n, a(n) for n = 1..10000</a>
%e a(1)=#{0}=1, (2^0 + 1) mod 1;
%e a(17) = #{4, 12} = 2, (2^4 + 1) mod 17 = (2^12 + 1) mod 17 = 0;
%e a(18) = #{} = 0;
%e a(19) = #{9} = 1, (2^9 + 1) mod 19 = 0.
%t nn = 100; pwrs = 2^Range[0, nn] + 1; Table[cnt = 0; Do[If[Mod[pwrs[[i]], n] == 0, cnt++], {i, n}]; cnt, {n, nn}] (* _T. D. Noe_, Sep 30 2011 *)
%o (Haskell)
%o a195470 n = length $ filter ((== 0) . (`mod` n)) $
%o take (fromInteger n) a000051_list
%Y Cf. A000051, A195610.
%K nonn
%O 1,17
%A _Reinhard Zumkeller_, Sep 21 2011
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