OFFSET
1,2
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. P. Stanley, Ordered structures and partitions, Memoirs of the Amer. Math. Soc., no. 119 (1972).
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
R. P. Stanley, A Fibonacci lattice, Fib. Quart., 13 (1975), 215-232.
FORMULA
G.f.: (1-x)^6/Product_{i=1..6} (1-x-x^i+x^(1+2*i)) - 1. - Emeric Deutsch, Dec 19 2004
MAPLE
G:=(1-x)^6/Product(1-x-x^i+x^(1+2*i), i=1..6)-1: Gser:=series(G, x=0, 39): seq(coeff(Gser, x^n), n=1..37); # Emeric Deutsch, Dec 19 2004
MATHEMATICA
CoefficientList[Series[(1-x)^6/Product[1-x-x^i+x^(1+2i), {i, 6}]-1, {x, 0, 40}], x] (* Harvey P. Dale, Jan 23 2015 *)
PROG
(Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( -1 + (1-x)^6/(&*[1-x-x^j+x^(2*j+1): j in [1..6]]) )); // G. C. Greubel, Nov 19 2022
(SageMath)
def A005407_list(prec):
P.<x> = PowerSeriesRing(ZZ, prec)
return P( -1 + (1-x)^6/product(1-x-x^j+x^(2*j+1) for j in (1..6)) ).list()
a=A005407_list(50); a[1:] # G. C. Greubel, Nov 19 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Emeric Deutsch, Dec 19 2004
STATUS
approved