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 A294793 Triangle read by rows, 1 <= k <= n: T(n,k) = non-isomorphic colorings of a toroidal n X k grid using exactly four colors under translational symmetry and swappable colors. 8
 0, 0, 1, 0, 13, 874, 1, 235, 51075, 10741819, 2, 3437, 2823766, 2261625725, 1870851589562, 13, 51275, 155495153, 486711524815, 1600136051453135, 5465007068038102643, 50, 742651, 8643289534, 107092397450897, 1405227969932349726, 19188864521773558375127, 269482732023591671431784330, 221, 10741763, 486710971595, 24009547064476683 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS Two colorings are equivalent if there is a permutation of the colors that takes one to the other in addition to translational symmetries on the torus. (Power Group Enumeration.) REFERENCES F. Harary and E. Palmer, Graphical Enumeration, Academic Press, 1973. LINKS Marko Riedel et al., Burnside lemma and translational symmetries of the torus. FORMULA T(n,k) = (1/(n*k*Q!))*(Sum_{sigma in S_Q} Sum_{d|n} Sum_{f|k} phi(d) phi(f) [[forall j_l(sigma) > 0 : l|lcm(d,f) ]] P(gcd(d,f)*(n/d)*(k/f), sigma)) where P(F, sigma) = F! [z^F] Product_{l=1..Q} (exp(lz)-1)^j_l(sigma) with Q=4. The notation j_l(sigma) is from the Harary text and gives the number of cycles of length l in the permutation sigma. [[.]] is an Iverson bracket. CROSSREFS Cf. A294684, A294685, A294686, A294687, A294791, A294792, A294794, A295197. T(n,1) is A056297. Sequence in context: A289225 A331341 A123838 * A013539 A201255 A196695 Adjacent sequences:  A294790 A294791 A294792 * A294794 A294795 A294796 KEYWORD nonn,tabl AUTHOR Marko Riedel, Nov 08 2017 STATUS approved

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Last modified August 10 04:38 EDT 2020. Contains 336368 sequences. (Running on oeis4.)