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%I #11 Jun 16 2013 14:16:09
%S 2857,57,1,22857,457,9,182857,3657,73,1462857,29257,585,11702857,
%T 234057,4681,93622857,1872457,37449,748982857,14979657,299593,
%U 5991862857,119837257,2396745,47934902857,958698057,19173961
%N Terms in the decimal expansion of 1/(7*5^n) before the block of decimals 142857 (the period of 1/7) appears.
%C Example: 1/(7*5^4)=0.00022857(142857) hence a(4)=22857
%F Empirical g.f.: x*(-56*x^2-2800*x+2857) / (8*x^4-8*x^3-x+1). - _Colin Barker_, Jun 16 2013
%o (PARI) a(n)=if(n<0, 0, s=1; while(frac(10^s/7/5^n-1/7)>0, s++); floor(10^s/7/5^n)) \\ _Colin Barker_, Jun 16 2013
%Y Cf. A067556.
%K nonn,base
%O 1,1
%A _Benoit Cloitre_, Feb 05 2002; revised Dec 11, 2004
%E a(12) corrected by _Colin Barker_, Jun 16 2013