A087675 Consider recurrence b(0) = (2n+1)/2, b(n) = b(0)*floor(b(n-1)); sequence gives first integer reached.

5, 35, 18, 814, 39, 390, 68, 72827, 105, 1449, 150, 31887, 203, 3596, 264, 27852510, 333, 7215, 410, 208464, 495, 12690, 588, 10561998, 689, 20405, 798, 744049, 915, 30744, 1040, 46620858503, 1173, 44091, 1314, 1950450, 1463, 60830, 1620, 121575329, 1785

Offset

2,1

Links

Robert Israel, Table of n, a(n) for n = 2..10000

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

Formula

The even-indexed terms are given by A007742.

Maple

f:= proc(n)
  local b0, b;
  b0:= (2*n+1)/2;
  b:= b0;
  do
    b:= b0*floor(b);
    if b::integer then return b fi
  od
end proc:
map(f, [$2..100]); # Robert Israel, Nov 25 2019

Mathematica

f[n_] := Module[{b0, b}, b0 = (2n+1)/2; b = b0; While[True, b = b0*Floor[b]; If[IntegerQ[b], Return[b]]]];
Table[f[n], {n, 2, 100}] (* Jean-François Alcover, Oct 23 2023, after Robert Israel *)

Crossrefs

A001511 gives number of steps to reach an integer.

Cf. A001511, A081853, A085071, A057016.

Sequence in context: A095865 A199359 A199584 * A376610 A128044 A299529

Adjacent sequences: A087672 A087673 A087674 * A087676 A087677 A087678

Keyword

nonn,look

Author

N. J. A. Sloane, following a suggestion of Bela Bajnok (bbajnok(AT)gettysburg.edu), Sep 27 2003

Extensions

Offset corrected by Robert Israel, Nov 25 2019

Status

approved