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Index of 7^n within sequence of numbers of form 7^i*10^j.
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%I #5 Mar 30 2012 18:35:28

%S 1,2,4,7,11,16,22,28,35,43,52,62,73,84,96,109,123,138,154,171,188,206,

%T 225,245,266,288,310,333,357,382,408,435,463,491,520,550,581,613,646,

%U 679,713,748,784,821,859,898,937,977,1018,1060,1103,1147,1191,1236,1282,1329

%N Index of 7^n within sequence of numbers of form 7^i*10^j.

%K nonn

%O 1,2

%A _David W. Wilson_