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 A087507 #{0<=k<=n: kn 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 COMMENTS A087507(n)+A087508(n)+A087509(n)=A000027(n) LINKS 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. CROSSREFS Sequence in context: A023634 A199609 A019834 * A020777 A153810 A098134 Adjacent sequences:  A087504 A087505 A087506 * A087508 A087509 A087510 KEYWORD easy,nonn AUTHOR Paul Barry, Sep 11 2003 STATUS approved

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