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.

Showing 1-3 of 3 results.

A087667 Records in A087664.

Original entry on oeis.org

0, 2, 4, 5, 9, 12, 16, 24, 29, 30, 31, 32, 36, 37, 42
Offset: 1

Views

Author

N. J. A. Sloane, Sep 27 2003

Keywords

Crossrefs

Cf. A087664, A087668.

Programs

  • PARI
    A087664(n)={ local(x,s) ; x=n/4 ; s=0 ; while( type(x)!="t_INT", x *= floor(x) ; s++ ; ) ; return(s) ; } { rec=-1 ; for(n=8,1000000, a=A087664(n) ; if(a>rec, rec=a ; print(rec) ; ) ; ) ; } - R. J. Mathar, Nov 25 2006

Formula

a(n)=A087664(A087668(n)). - R. J. Mathar, Nov 25 2006

Extensions

More terms from R. J. Mathar, Nov 25 2006
a(8)-a(15) from Max Alekseyev, Jul 30 2011

A087668 Indices of records in A087664.

Original entry on oeis.org

8, 9, 11, 13, 15, 133, 2317, 39845, 108167, 46779959, 70246181, 248897669, 452691117, 1137506437, 3089581031
Offset: 1

Views

Author

N. J. A. Sloane, Sep 27 2003

Keywords

Comments

No other terms below 10^10.

Crossrefs

Cf. A087664, A087667.

Programs

  • PARI
    A087664(n)={ local(x,s) ; x=n/4 ; s=0 ; while( type(x)!="t_INT", x *= floor(x) ; s++ ; ) ; return(s) ; } { rec=-1 ; for(n=8,1000000, a=A087664(n) ; if(a>rec, rec=a ; print(n) ; ) ; ) ; } - R. J. Mathar, Nov 25 2006

Extensions

More terms from R. J. Mathar, Nov 25 2006
a(9)-a(15) from Max Alekseyev, Jul 30 2011

A087665 Consider recurrence b(0) = n/4, b(k) = b(k-1)*floor(b(k-1)); sequence gives first integer reached, or -1 if no integer is ever reached.

Original entry on oeis.org

2, 18, 5, 550935, 3, 3396542576998428, 105
Offset: 8

Views

Author

N. J. A. Sloane, Sep 27 2003

Keywords

Comments

It is conjectured that an integer is always reached if the initial value is >= 2.
a(133) has 6227 digits. - Michael S. Branicky, Feb 18 2021

Links

Crossrefs

Cf. A087664 (steps to reach an integer), A087667, A087668.

Programs

  • Python
    from fractions import Fraction
def a(n):
  b = Fraction(n, 4)
  while b.denominator != 1: b *= int(b)
  return b
for n in range(8, 15): print(a(n)) # Michael S. Branicky, Feb 18 2021

Extensions

The next term is too large to include.
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.