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A130544 Multiplicative persistence of n!!. 1
0, 0, 0, 0, 0, 1, 2, 1, 4, 2, 1, 1, 1, 3, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,7

COMMENTS

From 24!! on all the numbers have same digits equal to zero thus the persistence is equal to 1.

LINKS

Table of n, a(n) for n=0..100.

EXAMPLE

6!!= 6*4*2= 48 --> 4*8=32 --> 3*2= 6 --> Persistence=2

13!!=135135 --> 1*3*5*1*3*5=225 -->2*2*5=20 --> 2*0=0 --> Persistence=3

MAPLE

P:=proc(n) local i, k, w, ok, cont; for i from 0 by 1 to n do k:=i; w:=i-2; while w>0 do k:=k*w; w:=w-2; od; w:=1; ok:=1; if k<10 then print(0); else cont:=1; while ok=1 do while k>0 do w:=w*(k-(trunc(k/10)*10)); k:=trunc(k/10); od; if w<10 then ok:=0; print(cont); else cont:=cont+1; k:=w; w:=1; fi; od; fi; od; end: P(100);

CROSSREFS

Cf. A031346, A130543.

Sequence in context: A016445 A244554 A194735 * A214027 A007739 A290935

Adjacent sequences:  A130541 A130542 A130543 * A130545 A130546 A130547

KEYWORD

easy,nonn,base

AUTHOR

Paolo P. Lava and Giorgio Balzarotti, Jun 04 2007

STATUS

approved

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Last modified February 20 21:09 EST 2019. Contains 320350 sequences. (Running on oeis4.)