

A092437


Triangle read by rows, arising from enumeration of domino tilings of Aztec Pillowlike regions.


6



1, 1, 1, 2, 1, 1, 5, 6, 6, 1, 1, 5, 13, 26, 30, 20, 1, 1, 5, 13, 41, 90, 140, 140, 70, 1, 1, 5, 13, 41, 121, 302, 560, 742, 630, 252
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OFFSET

0,4


COMMENTS

The rows are of lengths 1, 3, 5, 7, ...
In particular, the rows are 1; 1,1,2; 1,1,5,6,6; 1,1,5,13,26,30,20; ... etc.
Call the first row row 0 and entries starting from 0. Then entries i=0 through k in row k are A046717(i).
In row k, entry k+1 is sequence A092438 and entry k+2 is sequence A092439.
In row k, entry 2k1 is A002457(k1) and entry 2k is A000984(k).


REFERENCES

J. Propp, Enumeration of matchings: problems and progress, pp. 255291 in L. J. Billera et al., eds, New Perspectives in Algebraic Combinatorics, Cambridge, 1999 (see Problem 13).


LINKS

Table of n, a(n) for n=0..35.
J. Propp, Publications and Preprints
J. Propp, Enumeration of matchings: problems and progress, in L. J. Billera et al. (eds.), New Perspectives in Algebraic Combinatorics


CROSSREFS

Cf. A092438A092443.
Sequence in context: A266681 A210664 A176093 * A064814 A051012 A064644
Adjacent sequences: A092434 A092435 A092436 * A092438 A092439 A092440


KEYWORD

hard,nonn,tabf


AUTHOR

Christopher Hanusa (chanusa(AT)math.washington.edu), Mar 24 2004


STATUS

approved



