cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A277533 Value of decimal number corresponding to the string of equal digits starting at position A277532(n) after the decimal point in the decimal expansion of the Euler-Mascheroni constant.

Original entry on oeis.org

5, 77, 777, 0, 0, 333333
Offset: 1

Views

Author

Felix Fröhlich, Oct 19 2016

Keywords

Crossrefs

Programs

  • PARI
    emstring(n) = default(realprecision, n+10); my(x=Euler); floor(x*10^n)
    emdigit(n) = emstring(n)-10*emstring(n-1)
    searchstrval(n) = my(x=1, i=1); while(1, my(y=x+1); while(emdigit(y)==emdigit(x), y++; i++); if(i >= n, return(emdigit(x)*(10^n-1)/9)); i=1; x++)
    a(n) = searchstrval(n)

Formula

a(n) = A001620(A277532(n)) * A002275(n).

A280546 Index in A002193 of start of first occurrence of at least n consecutive equal digits in the decimal expansion of sqrt(2) after the decimal point.

Original entry on oeis.org

2, 19, 150, 953, 2708, 32414, 158810, 4602784, 472173970, 472173970
Offset: 1

Views

Author

Felix Fröhlich, Jan 05 2017

Keywords

Comments

We index the digits of sqrt(2) = 1.4142135... starting with 1 (for the 1), 2 (for the 4), 3 (for the second 1), 4 (for the second 4), 5 (for the 2), and so on.
Find the index of the first digit of a run of n consecutive equal digits after the decimal point: this is a(n). For example, the "88" here 1414213562373095048801.. begins at the 19th digit, so a(2) = 19. - N. J. A. Sloane, Mar 20 2023

Crossrefs

Programs

  • Mathematica
    Module[{nn=160000,s2},s2=RealDigits[Sqrt[2],10,nn][[1]];Flatten[Table[ SequencePosition[ s2,PadRight[{},k,x_],1],{k,7}],1]][[;;,1]] (* Harvey P. Dale, Mar 20 2023 *)
  • PARI
    string(n) = default(realprecision, n+10); my(x=sqrt(2)); floor(x*10^n)
    digit(n) = string(n)-10*string(n-1)
    searchstrpos(n) = my(x=1, i=1); while(1, my(y=x+1); while(digit(y)==digit(x), y++; i++); if(i >= n, return(x+1)); i=1; x++)
    a(n) = searchstrpos(n)
Showing 1-2 of 2 results.