cp's OEIS Frontend

Examples

			For n = 2 with the board
+---+---+
| 1 | 1 |
+---+---+
| 2 | 2 |
+---+---+
| 3 | 3 |
+---+---+
| 4 | 4 |
+---+---+
There is only 1 solution being the squares with these letters:
+---+---+
| A | B |
+---+---+
| C | D |
+---+---+
| E | F |
+---+---+
| G | H |
+---+---+
Solution:
1) AB - CD - EF - GH
There is one solution so a(2) = 1.
.
For n = 3 with the board
+---+---+---+
| 1 | 2 | 2 |
+---+---+---+
| 1 | 2 | 2 |
+---+---+---+
| 3 | 4 | 4 |
+---+---+---+
| 3 | 4 | 4 |
+---+---+---+
the maximum number of solutions is 31 being the squares with these letters:
+---+---+---+
| A | B | C |
+---+---+---+
| D | E | F |
+---+---+---+
| G | H | I |
+---+---+---+
| J | K | L |
+---+---+---+
Solutions:
  1)	AD - GJ - BC - HEFILK
  2)	AD - GJ - BC - IFEHKL
  3)	AD - GJ - BC - KHEFIL
  4)	AD - GJ - KL - EHIFCB
  5)	AD - GJ - KL - FIHEBC
  6)	AD - GJ - KL - BEHIFC
  7)	AD - GJ - BCFE - HILK
  8)	AD - GJ - BCFE - ILKH
  9)	AD - GJ - BCFE - LKHI
  10)	AD - GJ - BCFE - KHIL
  11)	AD - GJ - CFEB - HILK
  12)	AD - GJ - CFEB - ILKH
  13)	AD - GJ - CFEB - LKHI
  14)	AD - GJ - CFEB - KHIL
  15)	AD - GJ - FEBC - HILK
  16)	AD - GJ - FEBC - ILKH
  17)	AD - GJ - FEBC - LKHI
  18)	AD - GJ - FEBC - KHIL
  19)	AD - GJ - EBCF - HILK
  20)	AD - GJ - EBCF - ILKH
  21)	AD - GJ - EBCF - LKHI
  22)	AD - GJ - EBCF - KHIL
  23)	ABED - GJ - CF - HILK
  24)	ABED - GJ - CF - ILKH
  25)	ABED - GJ - CF - LKHI
  26)	ABED - GJ - CF - KHIL
  27)	GHKJ - AD - IL - BCFE
  28)	GHKJ - AD - IL - CFEB
  29)	GHKJ - AD - IL - FEBC
  30)	GHKJ - AD - IL - EBCF
  31)	ABED - GHKJ - CF - IL
There are 31 solutions so a(3) = 31.