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A002890 Low temperature series for spin-1/2 Ising partition function on 2D square lattice.
(Formerly M1463 N0578)
6
1, 0, 1, 2, 5, 14, 44, 152, 566, 2234, 9228, 39520, 174271, 787246, 3628992, 17019374, 81011889, 390633382, 1905134695, 9385453576, 46653815395, 233788460256, 1180111379105, 5996452414310, 30653752894948 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

REFERENCES

S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 391-406.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Andrey Zabolotskiy, Table of n, a(n) for n = 0..500

P. D. Beale, Exact distribution of energies in the two-dimensional Ising model, Phys. Rev. Lett. 76 (1996) 78-81

C. Domb, On the theory of cooperative phenomena in crystals, Advances in Phys., 9 (1960), 149-361.

Steven R. Finch, Lenz-Ising Constants [broken link]

Steven R. Finch, Lenz-Ising Constants [From the Wayback Machine]

G. Siudem, A. Fronczak, and P. Fronczak, Exact low-temperature series expansion for the partition function of the two-dimensional zero-field s= 1/2 Ising model on the infinite square lattice, arXiv preprint arXiv:1410.7963 [math-ph], 2014-2015.

Gandhimohan M. Viswanathan, The hypergeometric series for the partition function of the 2-D Ising model arXiv:1411.2495 [cond-mat.stat-mech], 2014-2015.

Gandhimohan M. Viswanathan, The double hypergeometric series for the partition function of the 2D anisotropic Ising model, arXiv:2104.03430 [cond-mat.stat-mech], 2021.

MATHEMATICA

(* For 25 terms, a PC computation lasts less than half an hour *) m = 48 (* max y exponent *); coes = CoefficientList[ Series[ Log[(1 + y^2)^2 - 2*y*(1 - y^2)*(Cos[2*Pi*u] + Cos[2*Pi*v])], {y, 0, m}], y] // Rest; nint[f_, {n_}] := If[n == 2 || OddQ[n], 0, Print[n]; Integrate[ Integrate[f, {u, 0, 1}], {v, 0, 1}]]; fy = MapIndexed[nint, coes].Table[y^k, {k, 1, m}]; CoefficientList[ Series[ Exp[fy/2], {y, 0, m}] , y^2] (* Jean-Fran├žois Alcover, Mar 19 2013 *)

CoefficientList[(1+u) Exp[-x HypergeometricPFQ[{1, 1, 3/2, 3/2}, {2, 2, 2}, 16x] /. {x -> (u (1 - u)^2)/(1 + u)^4}] + O[u]^50, u] (* Andrey Zabolotskiy, Feb 12 2022, using the g. f. from Gandhimohan M. Viswanathan, 2014-2015 *)

CROSSREFS

Cf. A002891.

Sequence in context: A148336 A257273 A119021 * A202856 A118929 A287252

Adjacent sequences:  A002887 A002888 A002889 * A002891 A002892 A002893

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

Corrections and updates from Steven Finch

"Free energy" changed back to "partition function" (basically the exponential of the free energy) in the name by Andrey Zabolotskiy, Feb 11 2022

STATUS

approved

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Last modified August 19 18:30 EDT 2022. Contains 356229 sequences. (Running on oeis4.)