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A296360
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Number of monohedral disk tilings of type C^t_{2n+1,3}.
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4
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116, 6402, 446930, 34121322, 2741227176, 227759341712, 19382568941318, 1679333068357460, 147541888215426742, 13107891004266127974, 1175188298096727647322, 106164291028322202227232, 9652457243380891557169712, 882443342536355491502025678
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OFFSET
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1,1
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LINKS
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FORMULA
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MATHEMATICA
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U[n_, k_] := DivisorSum[GCD[n, k], EulerPhi[#]*Binomial[(n + k)/#, n/#]/(n + k) &];
a[n_] := 2*Sum[U[i, 3*(4*n + 2 - i)], {i, 0, 4*n + 2}];
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PROG
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U(n, k)={sumdiv(gcd(n, k), d, eulerphi(d)*binomial((n+k)/d, n/d)/(n+k))}
a(n)={2*sum(i=0, 4*n+2, U(i, 3*(4*n+2-i)))} \\ Andrew Howroyd, Jan 09 2018
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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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