A201545 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

47, 281, 381, 399, 515, 648, 918, 928, 1303, 1538, 3746

Offset

1,1

Comments

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.

Links

Table of n, a(n) for n=1..11.

Dave Andersen, Pi-Search Page

Example

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.

Maple

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

Crossrefs

Cf. A000796, A057680.

Sequence in context: A358399 A231440 A142164 * A142774 A069760 A140043

Adjacent sequences: A201542 A201543 A201544 * A201546 A201547 A201548

Keyword

nonn,base

Author

Matthew Goers, Dec 02 2011

Status

approved