cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A328341 Number of geometrically distinct open knight's tours on a 4 X n chessboard.

Original entry on oeis.org

0, 0, 3, 0, 22, 186, 1603, 7772, 47478, 303278, 1671273, 9121582, 50322028, 270896326, 1426536267, 7454807822, 38607660199, 197696949844, 1003736587788, 5060326202622, 25334034892953, 126024078250318, 623383415637750, 3067618264121349, 15022847233751804, 73245459228339114
Offset: 1

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Author

Andrew Howroyd, Oct 12 2019

Keywords

Examples

			a(3) = 3 because there are two symmetric and one asymmetric tour:
  +----+----+----+----+   +----+----+----+----+   +----+----+----+----+
  |  8 | 11 |  6 |  3 |   |  1 |  4 |  7 | 10 |   |  1 |  4 |  7 | 10 |
  +----+----+----+----+   +----+----+----+----+   +----+----+----+----+
  |  1 |  4 |  9 | 12 |   |  8 | 11 |  2 |  5 |   | 12 |  9 |  2 |  5 |
  +----+----+----+----+   +----+----+----+----+   +----+----+----+----+
  | 10 |  7 |  2 |  5 |   |  3 |  6 |  9 | 12 |   |  3 |  6 | 11 |  8 |
  +----+----+----+----+   +----+----+----+----+   +----+----+----+----+

Links

Crossrefs

Cf. A079137, A123936, A169777, A328340.

Formula

a(2*n) = A123936(2*n)/2; a(2*n-1) = (A123936(2*n-1) + A328340(n))/2.
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