A195458 - OEIS

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A195458

a(n) = floor(sqrt(n) * a(n-1)), starting with 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.)