A027931 T(n, 2n-8), T given by A027926.

1, 2, 5, 13, 34, 88, 221, 530, 1204, 2587, 5270, 10220, 18955, 33775, 58060, 96647, 156299, 246280, 379051, 571103, 843944, 1225258, 1750255, 2463232, 3419366, 4686761, 6348772, 8506630, 11282393, 14822249, 19300198, 24922141

Offset

4,2

Links

G. C. Greubel, Table of n, a(n) for n = 4..1000

Index entries for linear recurrences with constant coefficients, signature (9,-36,84,-126,126,-84,36,-9,1).

Formula

a(n) = Sum_{k=0..4} binomial(n-k, 8-2*k). - Len Smiley, Oct 20 2001

G.f.: x^4*(1 -7*x +23*x^2 -44*x^3 +55*x^4 -44*x^5 +23*x^6 -7*x^7+ x^8) / (1-x)^9 . - R. J. Mathar, Oct 31 2015

Maple

A027931 := proc(n)
    add(binomial(n-k, 8-2*k), k=0..4) ;
end proc: # R. J. Mathar, Oct 31 2015

Mathematica

Sum[Binomial[Range[4, 40] -k, 8-2*k], {k, 0, 4}] (* G. C. Greubel, Sep 27 2019 *)

Prog

(PARI) vector(40, n, sum(k=0, 4, binomial(n+3-k, 8-2*k)) ) \\ G. C. Greubel, Sep 27 2019
(Magma) [&+[Binomial(n-k, 8-2*k): k in [0..4]] : n in [4..40]]; // G. C. Greubel, Sep 27 2019
(Sage) [sum(binomial(n-k, 8-2*k) for k in (0..4)) for n in (4..40)] # G. C. Greubel, Sep 27 2019
(GAP) List([4..40], n-> Sum([0..4], k-> Binomial(n-k, 8-2*k)) ); # G. C. Greubel, Sep 27 2019

Crossrefs

Cf. A027926, A228074.

Sequence in context: A252932 A318234 A371426 * A218481 A267905 A209230

Adjacent sequences: A027928 A027929 A027930 * A027932 A027933 A027934

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved