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!)
A068011 Number of subsets of {1,2,3,...,n} that sum to 0 mod 5. 1
1, 1, 1, 2, 4, 8, 14, 26, 52, 104, 208, 412, 820, 1640, 3280, 6560, 13112, 26216, 52432, 104864, 209728, 419440, 838864, 1677728, 3355456, 6710912, 13421792, 26843552, 53687104, 107374208, 214748416, 429496768, 858993472, 1717986944 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,4
COMMENTS
For n>2, a(n) = 2 * A068031(n).
LINKS
Sophie LeBlanc, Jan 20 2002, sci.math posting
FORMULA
s(k+1) = 2s(k) if k == 2, 3, or 4 mod 5, 2s(k)-2^(k/5) if k == 0 mod 5, 2s(k)-2^((k-1)/5) if k == 1 mod 5
Empirical G.f.: -(x^2-x+1)*(2*x^3+2*x^2-1) / ((2*x-1)*(2*x^5-1)). [Colin Barker, Dec 22 2012]
MAPLE
A068011_rec := proc(n); if(0 = n) then RETURN(1); fi; if(1 = (n mod 5)) then RETURN(2*A068011_rec(n-1)-2^((n-1)/5)); fi; if(2 = (n mod 5)) then RETURN(2*A068011_rec(n-1)-2^((n-2)/5)); fi; RETURN(2*A068011_rec(n-1)); end;
MATHEMATICA
LinearRecurrence[{2, 0, 0, 0, 2, -4}, {1, 1, 1, 2, 4, 8}, 40] (* Jean-François Alcover, Mar 06 2016 *)
CROSSREFS
5th row of A068009.
Sequence in context: A164169 A164166 A164161 * A048238 A048140 A179817
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 11 2002
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 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)