A103999 - OEIS

A103999

Square array T(M,N) read by antidiagonals: number of dimer tilings of a 2M x 2N Klein bottle.

1, 1, 1, 1, 6, 1, 1, 16, 34, 1, 1, 54, 196, 198, 1, 1, 196, 1666, 2704, 1154, 1, 1, 726, 16384, 64152, 37636, 6726, 1, 1, 2704, 171394, 1844164, 2549186, 524176, 39202, 1, 1, 10086, 1844164, 57523158, 220581904, 101757654, 7300804, 228486, 1

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

0,5

LINKS

Table of n, a(n) for n=0..44.

Cliff, Danny and Zoe Stoll, About Klein bottles

W. T. Lu and F. Y. Wu, Dimer statistics on the Moebius strip and the Klein bottle, arXiv:cond-mat/9906154 [cond-mat.stat-mech], 1999.

FORMULA

T(M, N) = Product_{m=1..M} Product_{n=1..N} ( 4sin(Pi*(4n-1)/(4N))^2 + 4sin(Pi*(2m-1)/(2M))^2 ).

EXAMPLE

Array begins:

1, 1, 1, 1, 1, 1, 1, ...

1, 6, 34, 198, 1154, 6726, 39202, ...

1, 16, 196, 2704, 37636, 524176, 7300804, ...

1, 54, 1666, 64152, 2549186, 101757654, 4064620168, ...

1, 196, 16384, 1844164, 220581904, 26743369156, 3252222705664, ...

1, 726,171394, 57523158, 21050622914, 7902001927776, 2988827208115522, ...

MATHEMATICA

T[m_, n_] := Product[4 Sin[(4k-1) Pi/(4n)]^2 + 4 Cos[j Pi/(2m+1)]^2, {j, 1, m}, {k, 1, n}] // Round;

Table[T[m-n, n], {m, 0, 9}, {n, 0, m}] // Flatten (* Jean-François Alcover, Aug 20 2018 *)

PROG

(PARI) default(realprecision, 120);

{T(n, k) = round(prod(a=1, n, prod(b=1, k, 4*sin((4*a-1)*Pi/(4*n))^2+4*sin((2*b-1)*Pi/(2*k))^2)))} \\ Seiichi Manyama, Jan 11 2021

CROSSREFS

Rows include A003499, A067902+2. Columns include A003500+2.

Main diagonal gives A340557.

Cf. A099390, A103997.

Sequence in context: A176560 A152602 A119726 * A154985 A157275 A157268

Adjacent sequences: A103996 A103997 A103998 * A104000 A104001 A104002

KEYWORD

nonn,tabl

AUTHOR

Ralf Stephan, Feb 26 2005

STATUS

approved