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A008814 Expansion of (1+x^7)/((1-x)^2*(1-x^7)). 9
1, 2, 3, 4, 5, 6, 7, 10, 13, 16, 19, 22, 25, 28, 33, 38, 43, 48, 53, 58, 63, 70, 77, 84, 91, 98, 105, 112, 121, 130, 139, 148, 157, 166, 175, 186, 197, 208, 219, 230, 241, 252, 265, 278, 291, 304, 317, 330, 343, 358, 373, 388, 403, 418, 433, 448, 465, 482, 499 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Number of 0..n arrays of 8 elements with zero second differences. - R. H. Hardin, Nov 16 2011

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (2,-1,0,0,0,0,1,-2,1).

FORMULA

G.f.: (1+x^7)/((1-x)^2*(1-x^7)).

a(n) = 2*a(n-1) -a(n-2) +a(n-7) -2*a(n-8) +a(n-9). - R. H. Hardin, Nov 16 2011

MAPLE

seq(coeff(series((1+x^7)/((1-x)^2*(1-x^7)), x, n+1), x, n), n = 0..70); # G. C. Greubel, Sep 12 2019

MATHEMATICA

CoefficientList[Series[(1+x^7)/(1-x)^2/(1-x^7), {x, 0, 70}], x] (* or *)

LinearRecurrence[{2, -1, 0, 0, 0, 0, 1, -2, 1}, {1, 2, 3, 4, 5, 6, 7, 10, 13}, 70] (* Harvey P. Dale, Dec 18 2012 *)

PROG

(PARI) a(n)=(n*(n+2)+[7, 11, 13, 13, 11, 7, 1][n%7+1])/7 \\ Charles R Greathouse IV, Nov 16 2011

(PARI) a(n)=(n*(n+2)+13-6*(n%7==6))\7  \\ Tani Akinari, Jul 25 2013

(MAGMA) R<x>:=PowerSeriesRing(Integers(), 70); Coefficients(R!( (1+x^7)/((1-x)^2*(1-x^7)) )); // G. C. Greubel, Sep 12 2019

(Sage)

def A008814_list(prec):

    P.<x> = PowerSeriesRing(ZZ, prec)

    return P((1+x^7)/((1-x)^2*(1-x^7))).list()

A008814_list(70) # G. C. Greubel, Sep 12 2019

(GAP) a:=[1, 2, 3, 4, 5, 6, 7, 10, 13];; for n in [10..70] do a[n]:=2*a[n-1]-a[n-2]+a[n-7]-2*a[n-8]+a[n-9]; od; a; # G. C. Greubel, Sep 12 2019

CROSSREFS

Cf. Expansions of the form (1+x^m)/((1-x)^2*(1-x^m)): A000290 (m=1), A000982 (m=2), A008810 (m=3), A008811 (m=4), A008812 (m=5), A008813 (m=6), this sequence (m=7), A008815 (m=8), A008816 (m=9), A008817 (m=10).

Sequence in context: A164947 A112881 A308019 * A005140 A176486 A017845

Adjacent sequences:  A008811 A008812 A008813 * A008815 A008816 A008817

KEYWORD

nonn,easy,changed

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms added by G. C. Greubel, Sep 12 2019

STATUS

approved

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Last modified September 20 10:10 EDT 2019. Contains 327229 sequences. (Running on oeis4.)