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a(n) = T(n,n), where T is the array in A026148.
0

%I #12 Sep 19 2019 19:14:17

%S 1,1,2,4,12,32,89,246,685,1912,5355,15038,42339,119484,337935,957738,

%T 2719539,7736208,22044444,62916696,179841270,514793944,1475586687,

%U 4234989242,12169352003,35009302296,100826681530,290683486132,838873595124

%N a(n) = T(n,n), where T is the array in A026148.

%Y Cf. A026148

%Y First differences of A026325 for n > 1.

%K nonn

%O 0,3

%A _Clark Kimberling_

%E a(0)-a(1) inserted and a(20) corrected by _Sean A. Irvine_, Sep 18 2019