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, 7359917674141970

Offset

1,2

Comments

Arises in two-dimensional dimer problem.

Links

Table of n, a(n) for n=1..17.

Crossrefs

Sequence in context: A244469 A386398 A006193 * A194724 A308650 A081343

Adjacent sequences: A139394 A139395 A139396 * A139398 A139399 A139400

Keyword

nonn,more,changed

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

Offset corrected and a(17) from Dominik Beck, Jul 11 2026

Status

approved