This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A087507 #{0<=k<=n: k*n is divisible by 3}. 4
 1, 1, 1, 4, 2, 2, 7, 3, 3, 10, 4, 4, 13, 5, 5, 16, 6, 6, 19, 7, 7, 22, 8, 8, 25, 9, 9, 28, 10, 10, 31, 11, 11, 34, 12, 12, 37, 13, 13, 40, 14, 14, 43, 15, 15, 46, 16, 16, 49, 17, 17, 52, 18, 18, 55, 19, 19, 58, 20, 20, 61, 21, 21, 64, 22, 22, 67, 23, 23, 70, 24, 24, 73, 25, 25, 76 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Colin Barker, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (0,0,2,0,0,-1). FORMULA a(n) = sum{k=0..n, if (mod(kn, 3)=0, 1, 0) }. a(n) = floor(n/3)(5/3+4/3cos(2Pi*/3))+1. a(n)+A087508(n)+A087509(n) = n. a(n) = 2*a(n-3)-a(n-6) for n>5. - Colin Barker, May 02 2015 G.f.: (2*x^3+x^2+x+1) / ((x-1)^2*(x^2+x+1)^2). - Colin Barker, May 02 2015 PROG (PARI) Vec((2*x^3+x^2+x+1)/((x-1)^2*(x^2+x+1)^2) + O(x^100)) \\ Colin Barker, May 02 2015 CROSSREFS Cf. A016777 (trisection). Sequence in context: A019834 A261557 A270809 * A020777 A153810 A098134 Adjacent sequences:  A087504 A087505 A087506 * A087508 A087509 A087510 KEYWORD easy,nonn AUTHOR Paul Barry, Sep 11 2003 STATUS approved

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

Last modified October 21 14:20 EDT 2019. Contains 328301 sequences. (Running on oeis4.)