OFFSET
1,5
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1275 (rows 1..50)
FORMULA
Equals 2*A001263 - A000012 as infinite lower triangular matrices; where A001263 = the Narayana triangle.
T(n,k) = 2*binomial(n-1, k-1) * binomial(n, k-1) / k - 1. - Andrew Howroyd, Aug 10 2018
EXAMPLE
First few rows of the triangle are:
1;
1, 1;
1, 5, 1;
1, 11, 11, 1;
1, 19, 39, 19, 1;
1, 29, 99, 99, 29, 1;
...
PROG
(PARI) T(n, k) = if(k<=n, 2*binomial(n-1, k-1) * binomial(n, k-1) / k - 1, 0); \\ Andrew Howroyd, Aug 10 2018
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Gary W. Adamson, Aug 30 2007
EXTENSIONS
a(20) corrected and terms a(56) and beyond from Andrew Howroyd, Aug 10 2018
STATUS
approved