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A025709 Index of 5^n within sequence of numbers of form 5^i*8^j. 1

%I

%S 1,2,4,7,11,15,20,26,33,40,48,57,67,78,89,101,114,128,142,157,173,190,

%T 208,226,245,265,286,307,329,352,376,400,425,451,478,506,534,563,593,

%U 624,655,687,720,754,789,824,860,897,935,973,1012,1052,1093,1135,1177,1220

%N Index of 5^n within sequence of numbers of form 5^i*8^j.

%o (PARI) a(n)=my(N=1); n+1+sum(i=1, n, logint(N*=5, 8)); \\ _Charles R Greathouse IV_, Jan 16 2018

%o (PARI) first(n)=my(s, N=1/5); vector(n+1, i, s+=logint(N*=5, 8)+1) \\ _Charles R Greathouse IV_, Jan 16 2018

%Y Differs from A025703 at a(84).

%K nonn

%O 1,2

%A _David W. Wilson_

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Last modified October 18 05:26 EDT 2019. Contains 328146 sequences. (Running on oeis4.)