A114571 a(n) is the smallest value k for which k!! >= n!.

1, 2, 4, 6, 8, 9, 11, 12, 14, 16, 18, 19, 21, 23, 24, 26, 28, 30, 31, 33, 35, 36, 38, 40, 42, 43, 45, 47, 48, 50, 52, 54, 55, 57, 59, 61, 62, 64, 66, 68, 69, 71, 73, 75, 76, 78, 80, 82, 84, 85, 87, 89, 91, 92, 94, 96, 98, 99, 101, 103, 105, 106, 108, 110, 112, 114, 115, 117

Offset

1,2

Links

Table of n, a(n) for n=1..68.

Example

a(6)=9 since m!!<6! for m<9, while 9!!>=6!.

Mathematica

Module[{df=Table[{i, i!!}, {i, 200}]}, Transpose[Table[SelectFirst[df, #[[2]]>= n!&], {n, 100}]][[1]]] (* Harvey P. Dale, Nov 05 2015 *)

Crossrefs

Sequence in context: A186354 A186149 A298861 * A376452 A050091 A184740

Adjacent sequences: A114568 A114569 A114570 * A114572 A114573 A114574

Keyword

easy,nonn

Author

Giovanni Resta, Feb 16 2006

Status

approved