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A184276
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Number of distinct n X 5 toroidal 0..3 arrays.
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2
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208, 104968, 71582944, 54975633976, 45035996274688, 38430716856090160, 33731189163354610720, 30223145490393217217464, 27509778650786228378836960, 25353012004564610547932704768, 23601349356976489220593165438048, 22153799929748597900945512768786000
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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T[n_, k_] := (1/(n*k))*Sum[Sum[EulerPhi[c]*EulerPhi[d]*4^(n*k/LCM[c, d]), {d, Divisors[k]}], {c, Divisors[n]}]; a[n_] := T[n, 5]; Array[a, 12] (* Jean-François Alcover, Nov 01 2017, after Andrew Howroyd *)
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PROG
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(PARI) a(n) = my(k=5); (1/(n*k)) * sumdiv(n, c, sumdiv(k, d, eulerphi(c) * eulerphi(d) * 4^(n*k/lcm(c, d)))); \\ Michel Marcus, Nov 01 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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