The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A112838 Small-number statistic from the enumeration of domino tilings of a 5-pillow of order n. 11
 1, 2, 5, 13, 13, 29, 34, 100, 130, 305, 361, 881, 1145, 2906, 3557, 8669, 10693, 26893, 33680, 83360, 102800, 254565, 317165, 790037, 980237, 2428298, 3011265, 7483801, 9301217, 23092857, 28646722, 71093860 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A 5-pillow is a generalized Aztec pillow. The 5-pillow of order n is a rotationally-symmetric region. It has a 2 X 2n central band of squares and then steps up from this band with steps of 5 horizontal squares to every 1 vertical square and steps down with steps of 1 horizontal square to every 1 vertical square. Plotting A112838(n+2)/A112838(n) gives an intriguing damped sine curve. REFERENCES C. Hanusa (2005). A Gessel-Viennot-Type Method for Cycle Systems with Applications to Aztec Pillows. PhD Thesis. University of Washington, Seattle, USA. LINKS EXAMPLE The number of domino tilings of the 5-pillow of order 6 is 1666=7^2*34. A112838(n)=34. CROSSREFS A112833 breaks down as A112834^2 times A112835, where A112835 is not necessarily squarefree. 3-pillows: A112833-A112835; 7-pillows: A112839-A112841; 9-pillows: A112842-A112844. Sequence in context: A336883 A067365 A189993 * A111296 A089728 A127987 Adjacent sequences:  A112835 A112836 A112837 * A112839 A112840 A112841 KEYWORD easy,nonn AUTHOR Christopher Hanusa (chanusa(AT)math.binghamton.edu), Sep 21 2005 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 2 08:31 EST 2021. Contains 349437 sequences. (Running on oeis4.)