OFFSET
1,2
COMMENTS
See A211701 for a discussion and guide to related sequences.
LINKS
Index entries for linear recurrences with constant coefficients, signature (-1,-1,0,1,2,2,1,0,-1,-1,-1).
FORMULA
a(n) = -a(n-1)-a(n-2)+a(n-4)+2*a(n-5)+2*a(n-6)+a(n-7)-a(n-9)-a(n-10)-a(n-11) for n>=12.
MATHEMATICA
f[n_, m_] := Sum[Floor[n/k], {k, 1, m}]
t = Table[f[n, 5], {n, 1, 90}] (* A211704 *)
FindLinearRecurrence[t]
Table[Total[Table[Floor[n/i], {i, 5}]], {n, 70}] (* or *) LinearRecurrence[ {-1, -1, 0, 1, 2, 2, 1, 0, -1, -1, -1}, {1, 3, 5, 8, 10, 13, 14, 17, 19, 22, 23}, 70] (* Harvey P. Dale, Jan 19 2015 *)
PROG
(Magma) [n+Floor(n/2)+Floor(n/3)+Floor(n/4)+Floor(n/5): n in [1..70]]; // Vincenzo Librandi, Jun 23 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Apr 19 2012
STATUS
approved