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A028452 Number of perfect matchings in graph P_{3} X P_{3} X P_{2n}. 4
1, 229, 117805, 64647289, 35669566217, 19690797527709, 10870506600976757, 6001202979497804657, 3313042830624031354513, 1829008840116358153050197, 1009728374600381843221483965, 557433823481589253332775648233, 307738670509229621147710358375321 (list; graph; refs; listen; history; text; internal format)



Also the number of tilings of a 3 x 3 x 2n box with 1 x 1 x 2 bricks. - Johan de Ruiter, Jul 15 2012


Alois P. Heinz, Table of n, a(n) for n = 0..300

Per Hakan Lundow, Computation of matching polynomials and the number of 1-factors in polygraphs, Research report, No 12, 1996, Department of Math., Umea University, Sweden.

Per Hakan Lundow, Enumeration of matchings in polygraphs, 1998.

R. J. Mathar, Tilings of rectangular regions by rectangular tiles: Counts derived from transfer matrices, arXiv:1406.7788 (2014), eq (38).

J. Propp, A reciprocity theorem for domino tilings, El. J. Combin. 8 (2001) #R18

J. de Ruiter, Counting Domino Coverings and Chessboard Cycles, 2010.


From Johan de Ruiter, Jul 15 2012: (Start)

a(n) = 679a(n-1) -76177a(n-2) +3519127a(n-3) -85911555a(n-4) +1235863045a(n-5) -11123194131a(n-6) +65256474997a(n-7) -257866595482a(n-8) +705239311926a(n-9) -1363115167354a(n-10) +1888426032982a(n-11) -1888426032982a(n-12) +1363115167354a(n-13) -705239311926a(n-14) +257866595482a(n-15) -65256474997a(n-16) +11123194131a(n-17) -1235863045a(n-18) +85911555a(n-19) -3519127a(n-20) +76177a(n-21) -679a(n-22) +a(n-23).

G.f.: (x^18 -446x^17 +36701x^16 -1267416x^15 +22828288x^14 -235207768x^13 +1443564488x^12 -5338083112x^11 +11818867674x^10 -15460884436x^9 +11818867674x^8 -5338083112x^7 +1443564488x^6 -235207768x^5 +22828288x^4 -1267416x^3 +36701x^2 -446x +1)/(-x^19 +675x^18 -73471x^17 +3221189x^16 -72583272x^15 +925908264x^14 -6971103216x^13 +31523058272x^12 -86171526770x^11 +142604534086x^10 -142604534086x^9 +86171526770x^8 -31523058272x^7 +6971103216x^6 -925908264x^5 +72583272x^4 -3221189x^3 +73471x^2 -675x +1).



Cf. A006253, A028454, A049507.

Sequence in context: A124684 A332740 A178673 * A072020 A177826 A122269

Adjacent sequences:  A028449 A028450 A028451 * A028453 A028454 A028455




Per H. Lundow



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Last modified January 16 21:00 EST 2021. Contains 340213 sequences. (Running on oeis4.)