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%I #6 Mar 30 2012 18:58:11
%S 1,1,1,1,1,1,1,20,20,1,1,84,1,84,1,1,220,84,84,220,1,1,455,924,1,924,
%T 455,1,1,816,5005,220,220,5005,816,1,1,1330,18564,5005,1,5005,18564,
%U 1330,1,1,2024,54264,48620,455,455,48620,54264,2024,1,1,2925
%N Symmetric matrix by antidiagonals: C(max(3i,3j),min(3i,3j)), i>=0, j>=0.
%e Northwest corner:
%e 1.....20....84....220
%e 20....1.....84....924
%e 84....84....1.....220
%e 455...5005..5005..455
%t f[i_, j_] := Binomial[Max[3 i - 3, 3 j - 3], Min[3 i - 3, 3 j - 3]]
%t TableForm[Table[f[i, j], {i, 1, 10}, {j, 1, 10}]]
%t Flatten[Table[f[i, n + 1 - i], {n, 1, 14}, {i, 1, n}]]
%Y Cf. A205456.
%K nonn,tabl
%O 1,8
%A _Clark Kimberling_, Jan 28 2012
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