OFFSET
1,4
REFERENCES
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
Gheorghe Coserea, Table of n, a(n) for n = 1..203
R. C. Mullin and P. J. Schellenberg, The enumeration of c-nets via triangulations, J. Combin. Theory, 4 (1968), 259-276.
FORMULA
a(n) = A290326(n+1,n). - Sean A. Irvine, Sep 29 2015
PROG
(PARI)
A290326(n, k) = {
if (n < 3 || k < 3, return(0));
sum(i=0, k-1, sum(j=0, n-1,
(-1)^((i+j+1)%2) * binomial(i+j, i)*(i+j+1)*(i+j+2)/2*
(binomial(2*n, k-i-1) * binomial(2*k, n-j-1) -
4 * binomial(2*n-1, k-i-2) * binomial(2*k-1, n-j-2))));
};
vector(22, n, A290326(n+1, n)) \\ Gheorghe Coserea, Jul 28 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected and extended by Sean A. Irvine, Sep 29 2015
Name changed by Gheorghe Coserea, Jul 23 2017
STATUS
approved