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A195470 Number of numbers k with 0 <= k < n such that 2^k + 1 is multiple of n. 4
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, 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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,17

COMMENTS

a(A014657(n)) > 0; for n > 1: a(A014661(n)) = 0.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1)=#{0}=1, (2^0 + 1) mod 1;

a(17) = #{4, 12} = 2, (2^4 + 1) mod 17 = (2^12 + 1) mod 17 = 0;

a(18) = #{} = 0;

a(19) = #{9} = 1, (2^9 + 1) mod 19 = 0.

MATHEMATICA

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 *)

PROG

(Haskell)

a195470 n = length $ filter ((== 0) . (`mod` n)) $

                       take (fromInteger n) a000051_list

CROSSREFS

Cf. A000051, A195610.

Sequence in context: A206479 A219484 A060396 * A324902 A252370 A045827

Adjacent sequences:  A195467 A195468 A195469 * A195471 A195472 A195473

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Sep 21 2011

STATUS

approved

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Last modified April 23 03:26 EDT 2019. Contains 322380 sequences. (Running on oeis4.)