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A083704
a(n)=sum(k=1,n,floor(r*floor(k/r))) where r=sqrt(3).
1
0, 0, 1, 2, 5, 8, 13, 19, 25, 33, 41, 51, 61, 73, 86, 99, 114, 129, 146, 163, 182, 202, 222, 244, 266, 290, 315, 340, 367, 394, 423, 452, 483, 515, 547, 581, 615, 651, 687, 725, 764, 803, 844, 885, 928, 971, 1016, 1062, 1108, 1156, 1204, 1254, 1305, 1356, 1409
OFFSET
0,4
COMMENTS
More generally if r is irrational 1<r<2 then sum(k=1,n,floor(r*floor(k/r))) = n(n-3)/2 + ceiling(n/r)
FORMULA
a(n) = n(n-3)/2 + ceiling(n/sqrt(3))
CROSSREFS
Sequence in context: A289751 A200274 A122221 * A111097 A027916 A054254
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jun 15 2003
STATUS
approved