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A078260
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a(n) = denominator(N), where N = 0.246...up to 2n (concatenation 2 to 2n of first n even numbers after decimal point).
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2
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5, 25, 500, 2500, 100000, 25000000, 5000000000, 125000000000, 50000000000000, 500000000000000, 500000000000000000, 6250000000000000000, 5000000000000000000000, 250000000000000000000000, 10000000000000000000000000, 1250000000000000000000000000, 500000000000000000000000000000
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OFFSET
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1,1
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LINKS
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PROG
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(PARI) a(n) = {my(s = ""); for (k=1, n, s = concat(s, Str(2*k))); denominator(eval(s)/10^(#s)); } \\ Michel Marcus, Jan 15 2019
(PARI) a(n) = c = concat(vector(n, i, Str(2*i))); denominator(eval(c) / 10^#Str(c)) \\ David A. Corneth, Jan 15 2019
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CROSSREFS
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Cf. A078257 (similar, with concatenation of 1 to n), A078261 (numerators).
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KEYWORD
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base,frac,nonn,easy
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AUTHOR
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EXTENSIONS
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a(5) and a(10) corrected, a(15)-a(17) from Charlie Neder, Jan 14 2019
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STATUS
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approved
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