OFFSET
1,4
COMMENTS
The sequence without the initial 0's is the 3-fold convolution of A002212(n), (n=1,2,...). - Emeric Deutsch, Mar 13 2004
LINKS
B. N. Cyvin et al., A class of polygonal systems representing polycyclic conjugated hydrocarbons: Catacondensed monoheptafusenes, Monat. f. Chemie, 125 (1994), 1327-1337.
S. J. Cyvin et al., Enumeration and Classification of Certain Polygonal Systems Representing Polycyclic Conjugated Hydrocarbons: Annelated Catafusenes, J. Chem. Inform. Comput. Sci., 34 (1994), 1174-1180.
FORMULA
G.f.: (zM)^3, where M = (1 - 3*z - sqrt(1 - 6*z + 5*z^2))/(2*z^2). - Emeric Deutsch, Mar 13 2004
a(n) = (3/(n+1))*Sum_{m=0..n-2} C(n+1,m)*C(2*n-2*m+2,n-m-2). - Vladimir Kruchinin Oct 18 2022
a(n) = A003517(n) * hypergeom([-n - 4, 2 - n], [-n - 1/2], -1/4). - Peter Luschny, Oct 23 2022
MAPLE
Z:=(1-8*z+24*z^2-16*z^3-(1-6*z+8*z^2)*sqrt(1-6*z+5*z^2))/2: Zser:=series(Z, z=0, 32): seq(coeff(Zser, z, n), n=4..26); # Zerinvary Lajos, Jan 01 2007
a := n -> A003517(n) * hypergeom([-n - 4, 2 - n], [-n - 1/2], -1/4):
seq(simplify(a(n)), n = 0..22); # Peter Luschny, Oct 23 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Emeric Deutsch, Mar 13 2004
STATUS
approved
