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A036405
a(n) = ceiling(n^2/7).
3
0, 1, 1, 2, 3, 4, 6, 7, 10, 12, 15, 18, 21, 25, 28, 33, 37, 42, 47, 52, 58, 63, 70, 76, 83, 90, 97, 105, 112, 121, 129, 138, 147, 156, 166, 175, 186, 196, 207, 218, 229, 241, 252, 265, 277, 290, 303, 316, 330, 343, 358, 372, 387, 402, 417, 433, 448
OFFSET
0,4
FORMULA
a(n) = +2*a(n-1) -a(n-2) +a(n-7) -2*a(n-8) +a(n-9). G.f.: x*(1+x)*(x^2-x+1)*(x^4-x^3+x^2-x+1) / ( (x^6+x^5+x^4+x^3+x^2+x+1)*(1-x)^3 ). [R. J. Mathar, Jul 06 2010]
MAPLE
A036405:=n->ceil(n^2/7): seq(A036405(n), n=0..100); # Wesley Ivan Hurt, Jan 16 2017
MATHEMATICA
Ceiling[Range[0, 60]^2/7] (* or *) LinearRecurrence[{2, -1, 0, 0, 0, 0, 1, -2, 1}, {0, 1, 1, 2, 3, 4, 6, 7, 10}, 60] (* Harvey P. Dale, Jun 23 2015 *)
CROSSREFS
Sequence in context: A163180 A341270 A091515 * A051424 A308632 A137606
KEYWORD
nonn,easy
STATUS
approved