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A078990
Triangle arising from (4,2) tennis ball problem, read by rows.
2
1, 1, 2, 3, 1, 4, 10, 16, 22, 1, 6, 21, 52, 105, 158, 211, 1, 8, 36, 116, 301, 644, 1198, 1752, 2306, 1, 10, 55, 216, 678, 1784, 4088, 8144, 14506, 20868, 27230, 1, 12, 78, 360, 1320, 4064, 10896, 25872, 55354, 105704, 183284, 260864, 338444, 1, 14, 105
OFFSET
0,3
COMMENTS
Length of row n = 2n+1. Rows have been reversed.
LINKS
D. Merlini, R. Sprugnoli and M. C. Verri, The tennis ball problem, J. Combin. Theory, A 99 (2002), 307-344 (Table A.1).
EXAMPLE
Triangle starts:
1;
1, 2, 3;
1, 4, 10, 16, 22;
1, 6, 21, 52, 105, 158, 211;
...
PROG
(PARI) T(n, k)=if(k<0 || k>2*n, 0, if(n<1, k==0, sum(j=0, k, (j+1)*T(n-1, k-j))))
CROSSREFS
Final diagonal gives A079489. Row sums give A066357(n+1).
Sequence in context: A130152 A211233 A084608 * A176566 A079639 A104694
KEYWORD
tabf,nonn
AUTHOR
N. J. A. Sloane, Jan 20 2003
STATUS
approved