A232997 Number of tilings of a fortress (or Penta-Aztec-Diamond) of order n.

1, 1, 5, 50, 625, 15625, 1953125, 488281250, 152587890625, 95367431640625, 298023223876953125, 1862645149230957031250, 14551915228366851806640625, 227373675443232059478759765625, 17763568394002504646778106689453125, 2775557561562891351059079170227050781250

Offset

0,3

Comments

The Lai (2013) article contains many other sequences which should be added to the OEIS (e.g. the sequences in Theorems 15, 18, 21, 22 and Corollary 20).

Links

Table of n, a(n) for n=0..15.

Tri Lai, New aspects of regions whose tilings are enumerated by perfect powers, Electronic Journal of Combinatorics, 20(4), 2013, #P31. See Th. 8.

Maple

f:=n-> if (n mod 2) = 0 then 5^((n/2)^2) elif (n mod 4) = 1 then 5^((n^2-1)/4) else 2*5^((n^2-1)/4); fi;
[seq(f(n), n=0..30)];

Crossrefs

Sequence in context: A233068 A237020 A156058 * A357405 A234464 A047736

Adjacent sequences: A232994 A232995 A232996 * A232998 A232999 A233000

Keyword

nonn

Author

N. J. A. Sloane, Dec 17 2013

Status

approved