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A172496 a(n) = numerator of fraction a/b, where gcd(a, b) = 1, whose decimal representation has the form 0.(1)(2)(3)...(n-1)(n)... with period (1)(2)(3)...(n-1)(n). 2

%I #11 Mar 31 2022 12:52:13

%S 1,4,41,1234,4115,41152,1234567,1371742,13717421,12345678910,

%T 411522630337,41152263033704,12345678910111213,411522630337040438,

%U 41152263033704043805,12345678910111213141516,137174210112346812683513,13717421011234681268351302

%N a(n) = numerator of fraction a/b, where gcd(a, b) = 1, whose decimal representation has the form 0.(1)(2)(3)...(n-1)(n)... with period (1)(2)(3)...(n-1)(n).

%C Denominators in A172498.

%H Alois P. Heinz, <a href="/A172496/b172496.txt">Table of n, a(n) for n = 1..369</a>

%e a(10) = 12345678910; 12345678910/99999999999 = 0.1234567891012345678910... (period 12345678910).

%p a:= n-> (m-> numer(m*sum(10^(-i*length(m)), i=1..infinity))

%p )(parse(cat(seq(i, i=1..n)))):

%p seq(a(n), n=1..19); # _Alois P. Heinz_, Mar 31 2022

%K nonn,base

%O 1,2

%A _Jaroslav Krizek_, Feb 05 2010

%E More terms from _Alois P. Heinz_, Mar 31 2022

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Last modified July 24 13:23 EDT 2024. Contains 374584 sequences. (Running on oeis4.)