A139397 Number of pyramids which can be constructed using n 1 x 2 tiles placed on an integral grid, with the base block at a fixed position.

1, 7, 58, 521, 4906, 47644, 472844, 4768953, 48699382, 502239812, 5221405608, 54645915476, 575131754640, 6082204395960, 64588573227268, 688370635513449

Offset

0,2

Comments

Arises in two-dimensional dimer problem.

Links

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

Crossrefs

Sequence in context: A334610 A244469 A006193 * A194724 A308650 A081343

Adjacent sequences: A139394 A139395 A139396 * A139398 A139399 A139400

Keyword

nonn,more

Author

Paul Federbush (PFED(AT)umich.edu), Jun 11 2008

Extensions

Added definition and more terms (computed by Rasmus Mølck Nilsson) submitted by Søren Eilers, Mar 27 2013

Status

approved