OFFSET
0,3
COMMENTS
In Williamson's terminology, this is "Number of 8-hoops with n symbols."
LINKS
Harry J. Smith, Table of n, a(n) for n=0..500
S. G. Williamson, The combinatorial analysis of patterns and the principle of inclusion-exclusion, Discrete Math. 1 (1972), no. 4, 357--388. MR0299493 (45 #8541). - N. J. A. Sloane, Mar 27 2012
FORMULA
a(n) = n*(n+1)*(n^6-n^5+n^4+3*n^3+2*n^2-2*n+4)/16.
G.f.: x*(1+21*x+264*x^2+949*x^3+1014*x^4+258*x^5+13*x^6)/(1-x)^9. [Colin Barker, Jan 29 2012]
PROG
(PARI) { for (n=0, 500, write("b060560.txt", n, " ", (n^8 + 4*n^5 + 5*n^4 + 2*n^2 + 4*n)/16); ) } \\ Harry J. Smith, Jul 07 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 12 2001
STATUS
approved