login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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
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
Sequence in context: A219484 A060396 A353353 * A324902 A252370 A045827
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Sep 21 2011
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 19 06:53 EDT 2024. Contains 370953 sequences. (Running on oeis4.)