OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 194
Index entries for linear recurrences with constant coefficients, signature (2,-1,0,0,0,0,0,0,0,0,1,-2,1).
FORMULA
From Mitch Harris, Sep 08 2008: (Start)
a(n) = Sum_{j=0..n+11} floor(j/11).
a(n-11) = (1/2)*floor(n/11)*(2*n - 9 - 11*floor(n/11)). (End)
a(n) = A218530(n+11). - Philippe Deléham, Apr 03 2013
From Chai Wah Wu, Jul 08 2016: (Start)
a(n) = 2*a(n-1) - a(n-2) + a(n-11) - 2*a(n-12) + a(n-13) for n > 12.
G.f.: 1/(1 - 2*x + x^2 - x^11 + 2*x^12 - x^13) = 1/((1-x)^3 *(1+x+x^2+x^3+x^4+x^5+x^6+x^7+x^8+x^9+x^10)). (End)
EXAMPLE
..1....2....3....4....5....6....7....8....9...10...11
.13...15...17...19...21...23...25...27...29...31...33
.36...39...42...45...48...51...54...57...60...63...66
.70...74...78...82...86...90...94...98..102..106..110
115..120..125..130..135..140..145..150..155..160..165
171..177..183..189..195..201..207..213..219..225..231
238..245..252..259..266..273..280..287..294..301..308
316..324..332..340..348..356..364..372..380..388..396
405..414..423..432..441..450..459..468..477..486..495
505..515..525..535..545..555..565..575..585..595..605
...
- Philippe Deléham, Apr 03 2013
MAPLE
g:= 1/((1-x)^2*(1-x^11)); gser:= series(g, x=0, 72); seq(coeff(gser, x, n), n=0..70); # modified by G. C. Greubel, Jul 30 2019
MATHEMATICA
CoefficientList[Series[1/((1-x)^2*(1-x^11)), {x, 0, 70}], x] (* Vincenzo Librandi, Jun 11 2013 *)
PROG
(PARI) my(x='x+O('x^70)); Vec(1/((1-x)^2*(1-x^11))) \\ G. C. Greubel, Jul 30 2019
(Magma) R<x>:=PowerSeriesRing(Integers(), 70); Coefficients(R!( 1/((1-x)^2*(1-x^11)) )); // G. C. Greubel, Jul 30 2019
(Sage) (1/((1-x)^2*(1-x^11))).series(x, 70).coefficients(x, sparse=False) # G. C. Greubel, Jul 30 2019
(GAP) a:=[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15];; for n in [14..70] do a[n]:=2*a[n-1]-a[n-2]+a[n-11]-2*a[n-12]+a[n-13]; od; a; # G. C. Greubel, Jul 30 2019
CROSSREFS
KEYWORD
nonn,tabf,easy
AUTHOR
EXTENSIONS
More terms from Vladimir Joseph Stephan Orlovsky, Mar 14 2010
STATUS
approved