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A025742
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a(n) is the index of 10^n within sequence of numbers of form 4^i*10^j.
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2
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1, 3, 7, 12, 19, 28, 38, 50, 64, 79, 96, 115, 135, 157, 181, 206, 233, 262, 292, 324, 358, 393, 430, 469, 509, 551, 595, 640, 687, 736, 786, 838, 892, 947, 1004, 1063, 1123, 1185, 1249, 1314, 1381, 1450, 1520, 1592, 1666, 1741, 1818, 1897, 1977, 2059, 2143, 2228
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OFFSET
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0,2
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COMMENTS
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LINKS
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EXAMPLE
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The index of 10^0 in A025621 is 1, so a(0)=1.
The index of 10^1 in A025621 is 3, so a(1)=3.
The index of 10^2 in A025621 is 7, so a(2)=7.
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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