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A195458 a(n) = floor(sqrt(n) * a(n-1)), starting with 1. 1
1, 1, 1, 2, 4, 8, 16, 32, 96, 288, 864, 2592, 7776, 23328, 69984, 279936, 1119744, 4478976, 17915904, 71663616, 286654464, 1146617856, 4586471424, 18345885696, 91729428480, 458647142400, 2293235712000, 11466178560000, 57330892800000, 286654464000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

a(n) = r(n+2)/sqrt(2); r(1) = sqrt(2); r(n) = r(n-1)/sqrt(n-1) if r(n-1) is a square else r(n) = r(n-1)*floor(sqrt(n-1).

A variation of Recamán's A008336.

LINKS

Table of n, a(n) for n=1..30.

MAPLE

r := proc(n) option remember; if n = 1 then sqrt(2)

elif type(r(n-1), square) then r(n-1)/sqrt(n-1)

else r(n-1)*floor(sqrt(n-1)) fi end:

A195458 := proc(n) r(n+2)/sqrt(2) end:

MATHEMATICA

a[1] = 1;

a[n_] := a[n] = Floor[Sqrt[n]] a[n - 1]

Table[a[n], {n, 20}] (* David Callan, Aug 14 2013 *)

CROSSREFS

Cf. A008336.

Sequence in context: A290555 A035523 A290301 * A264656 A078227 A250073

Adjacent sequences:  A195455 A195456 A195457 * A195459 A195460 A195461

KEYWORD

nonn

AUTHOR

Peter Luschny, Sep 18 2011

EXTENSIONS

Better name from David Callan, Aug 14 2013

STATUS

approved

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Last modified July 5 23:40 EDT 2022. Contains 355108 sequences. (Running on oeis4.)