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.

2, 18, 5, 550935, 3, 3396542576998428, 105

Offset

8,1

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

Michael S. Branicky, Table of n, a(n) for n = 8..132

J. C. Lagarias and N. J. A. Sloane, Approximate squaring (pdf, ps), Experimental Math., 13 (2004), 113-128.

Prog

(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

Crossrefs

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

Sequence in context: A253603 A094048 A179073 * A093481 A132629 A288161

Adjacent sequences: A087662 A087663 A087664 * A087666 A087667 A087668

Keyword

nonn

Author

N. J. A. Sloane, Sep 27 2003

Extensions

The next term is too large to include.

Status

approved