A026576 T(2n,n-2), T given by A026568.
1, 3, 18, 65, 346, 1288, 6818, 25518, 136152, 510532, 2745347, 10309234, 55784794, 209766714, 1140670242, 4294635438, 23445204441
Offset: 2
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