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%I #7 Jan 11 2018 10:08:06
%S 1,3,6,10,15,21,28,37,47,58,70,83,97,113,130,148,167,187,208,231,255,
%T 280,306,333,361,391,422,454,487,521,556,592,630,669,709,750,792,835,
%U 880,926,973,1021,1070,1120,1172,1225,1279,1334,1390,1447,1506,1566,1627,1689
%N Index of 5^n within sequence of numbers of form 4^i*5^j.
%H Charles R Greathouse IV, <a href="/A025706/b025706.txt">Table of n, a(n) for n = 0..10000</a>
%o (PARI) a(n)=my(N=1); n+1+sum(i=1, n, logint(N*=5, 4)); \\ _Charles R Greathouse IV_, Jan 11 2018
%o (PARI) first(n)=my(s, N=1/5); vector(n+1, i, s+=logint(N*=5, 4)+1) \\ _Charles R Greathouse IV_, Jan 11 2018
%Y Differs from A025730 at a(56).
%K nonn,easy
%O 0,2
%A _David W. Wilson_
%E Offset corrected by _Charles R Greathouse IV_, Jan 11 2018
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