A172505 - OEIS

A172505

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

%I #4 Apr 28 2019 17:58:47

%S 10,400,41000,12340000,411500000,41152000000

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

%C Sequence of denominators: 9, 33, 333, 9999, 33333, 333333, ... Conjecture: this sequence is not equal to the sequence A172498.

%e a(6) = 41152000000; 41152000000/333333 = 123456.123456123456... (period 123456).

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Feb 05 2010