OFFSET
1,1
LINKS
Matthew House, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (2,-1,0,0,0,0,0,0,1,-2,1).
FORMULA
G.f.: (2*x-x^2+x^4+x^7-x^9)/(1-2*x+x^2-x^9+2*x^10-x^11). - Matthew House, Feb 15 2017
a(n) = +2 a(n-1) -a(n-2) +a(n-9) -2 a(n-10) +a(n-11). - R. J. Mathar, Mar 11 2012
MATHEMATICA
a=9; b=-9;
Table[n+Floor[(a*n+b)^(1/2)], {n, 100}]
Table[n-1+Ceiling[(n^2-b)/a], {n, 90}]
Table[n+Ceiling[n^2/9], {n, 100}] (* or *) LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {2, 3, 4, 6, 8, 10, 13, 16, 18, 22, 25}, 100] (* Harvey P. Dale, Jun 25 2021 *)
PROG
(PARI) a(n)=a(n)=(n^2+9*n+8)\9 \\ Charles R Greathouse IV, Feb 15 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jan 09 2011
STATUS
approved