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A201545
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Numbers n such that the n-th digit (after the decimal point) in the decimal expansion of Pi are the occurrence of the least significant digit represented by the more significant digits
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0
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47, 281, 381, 399, 515, 648, 918, 928, 1303, 1538, 3746
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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The 47th digit after the decimal point in the expansion of Pi (A000796, but without the leading 3) is the 4th occurrence of the digit 7; the 281st is the 28th occurrence of the digit 1; etc.
Only individual least significant digits are included. Does not include, for example, 467, which is the beginning position of the 4th occurrence of 67.
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LINKS
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Table of n, a(n) for n=1..11.
Dave Andersen, Pi-Search Page
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EXAMPLE
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The 399th digit after the decimal point in Pi is the 39th occurrence of the digit 9.
225 is not in the sequence, as the 225th digit is 5, but this is the 23rd occurrence of the digit 5 in the expansion of pi, not the 22nd.
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MAPLE
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Digits := 4000 ;
pdg := proc(n)
floor(Pi*10^n) mod 10 ;
end proc:
dfreq := Vector(10, 0) ;
for n from 1 do
d := pdg(n) ;
dfreq[d+1] := dfreq[d+1]+1 ;
ld := n mod 10 ;
hid := floor(n/10) ;
if dfreq[d+1] = hid and ld = d then
print(n);
end if;
end do: # R. J. Mathar, Dec 16 2011
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CROSSREFS
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Cf. A000796, A057680.
Sequence in context: A358399 A231440 A142164 * A142774 A069760 A140043
Adjacent sequences: A201542 A201543 A201544 * A201546 A201547 A201548
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KEYWORD
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nonn,base
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AUTHOR
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Matthew Goers, Dec 02 2011
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STATUS
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approved
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