OFFSET
1,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..406
Sergey Fomin and Grigory Mikhalkin, Labeled floor diagrams for plane curves, arXiv:0906.3828 [math.AG], 2009-2010. [From N. J. A. Sloane, Sep 27 2010]
W. Trump, Magic series.
Eric Weisstein's World of Mathematics, Sinc Function
FORMULA
a(n) = (1/n) * Sum_{k=0, floor(n/2)} (-1)^k * binomial(n, k) * (n-2*k)^(n-1).
a(n) = A261398(n)/n. - Vladimir Reshetnikov, Sep 05 2016
MATHEMATICA
Table[1/n Sum[(-1)^k Binomial[n, k](n-2k)^(n-1), {k, 0, Floor[n/2]}], {n, 20}] (* Harvey P. Dale, Oct 21 2011 *)
PROG
(PARI) a(n)=(1/n)*sum(k=0, floor(n/2), (-1)^k*binomial(n, k)*(n-2*k)^(n-1))
(Magma) [(1/n)*(&+[(-1)^j*Binomial(n, j)*(n-2*j)^(n-1): j in [0..Floor(n/2)]]): n in [1..25]]; // G. C. Greubel, Apr 01 2022
(Sage) [(1/n)*sum((-1)^j*binomial(n, j)*(n-2*j)^(n-1) for j in (0..(n//2))) for n in (1..25)] # G. C. Greubel, Apr 01 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Nov 11 2004, Dec 11 2007
STATUS
approved