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, 4026, 4812, 7347, 15911, 19129, 19191, 26709, 27249, 27959, 28299, 29820, 34009, 36089, 36989, 37169, 38989, 39700, 39710, 39720, 39869, 41970, 42170, 43950, 44627, 51686, 52486, 52526, 52836, 54639, 54769

Offset: 1

Author

Matthew Goers, Dec 02 2011

Keywords

• nonn
• base

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.

Examples

			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.
		

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..10000
• Dave Andersen, Pi-Search Page
• Michael S. Branicky, Python program for OEIS A201545

Crossrefs

Cf. A000796, A057680.

Programs

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

Extensions

a(12) and beyond from Michael S. Branicky, Mar 06 2025