OFFSET
0,2
COMMENTS
Number of nodes degree 10 in virtual, optimal chordal graphs of diameter d(G)=n - S. Bujnowski & B. Dubalski (slawb(AT)atr.bydgoszcz.pl), Mar 07 2002
If Y_i (i=1,2,3,4,5) are 2-blocks of a (n+5)-set X then a(n-5) is the number of 10-subsets of X intersecting each Y_i (i=1,2,3,4,5). - Milan Janjic, Oct 28 2007
Equals binomial transform of [1, 10, 40, 80, 80, 32, 0, 0, 0, ...] where (1, 10, 40, 80, 80, 32) = row 5 of the Chebyshev triangle A013609. - Gary W. Adamson, Jul 19 2008
a(n) is the number of points in Z^5 that are L1 (Manhattan) distance <= n from any given point. Equivalently, due to a symmetry that is easier to see in the Delannoy numbers array (A008288), as a special case of Dmitry Zaitsev's Dec 10 2015 comment on A008288, a(n) is the number of points in Z^n that are L1 (Manhattan) distance <= 5 from any given point. - Shel Kaphan, Jan 02 2023
REFERENCES
L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 81.
E. Deza and M. M. Deza, Figurate numbers, World Scientific Publishing (2012), page 231.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
T. D. Noe, Table of n, a(n) for n = 0..1000
D. Bump, K. Choi, P. Kurlberg, and J. Vaaler, A local Riemann hypothesis, I pages 16 and 17
J. H. Conway and N. J. A. Sloane, Low-Dimensional Lattices VII: Coordination Sequences, Proc. Royal Soc. London, A453 (1997), 2369-2389 (pdf).
Milan Janjic, Two Enumerative Functions. [Broken link; WayBackMachine archive]
G. Kreweras, Sur les hiérarchies de segments, Cahiers du Bureau Universitaire de Recherche Opérationnelle, Institut de Statistique, Université de Paris, #20 (1973).
G. Kreweras, Sur les hiérarchies de segments, Cahiers du Bureau Universitaire de Recherche Opérationnelle, Institut de Statistique, Université de Paris, #20 (1973). (Annotated scanned copy)
Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.
Simon Plouffe, 1031 Generating Functions, Appendix to Thesis, Montreal, 1992
R. G. Stanton and D. D. Cowan, Note on a "square" functional equation, SIAM Rev., 12 (1970), 277-279.
Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).
FORMULA
G.f.: (1+x)^5 /(1-x)^6.
a(n) = (4*n^5+10*n^4+40*n^3+50*n^2+46*n+15)/15. - S. Bujnowski & B. Dubalski (slawb(AT)atr.bydgoszcz.pl), Mar 07 2002
a(n) = Sum_{k=0..min(5,n)} 2^k * binomial(5,k)* binomial(n,k). See Bump et al. - Tom Copeland, Sep 05 2014
E.g.f.: exp(x)*(15 + 150*x + 300*x^2 + 200*x^3 + 50*x^4 + 4*x^5)/15. - Stefano Spezia, Mar 17 2024
Sum_{n >= 1} (-1)^(n+1)/(n*a(n-1)*a(n)) = 47/60 - log(2) = (1 - 1/2 + 1/3 - 1/4 + 1/5) - log(2). - Peter Bala, Mar 23 2024
EXAMPLE
a(5)=1683, (4*5^5 + 10*5^4 + 40*5^3 + 50*5^2 + 46*5 + 15)/15 = (12500 + 6250 + 5000 + 230 + 15)/15 = 25245/15 = 1683.
MAPLE
for n from 1 to k do eval((4*n^5+10*n^4+40*n^3+50*n^2+46*n+15)/15) od;
A001847:=(z+1)**5/(z-1)**6; # conjectured by Simon Plouffe in his 1992 dissertation
MATHEMATICA
CoefficientList[Series[(z+1)^5/(z-1)^6, {z, 0, 200}], z] (* Vladimir Joseph Stephan Orlovsky, Jun 19 2011 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved