Even minus odd extensions of truncated 3 X 2n grid diagram.

A007724

Even minus odd extensions of truncated 3 X 2n grid diagram.

Terms

    a(0) =2a(1) =12a(2) =110a(3) =1274a(4) =17136a(5) =255816a(6) =4124406a(7) =70549050a(8) =1264752060a(9) =23555382240a(10) =452806924752

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