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A130634
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Additive persistence of double factorials.
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0
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0, 0, 0, 0, 0, 1, 2, 1, 2, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 4, 3, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 4, 3, 3, 4, 3, 4, 3, 4, 3, 4, 3, 3, 3, 3, 3, 3
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,7
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EXAMPLE
| 10!! = 10*8*6*4*2 = 3840 -> 3+8+4+0 = 15 -> 1+5 = 6 -> persistence = 2.
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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:=0; 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);
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CROSSREFS
| Cf. A001147.
Sequence in context: A115756 A067731 A147844 * A053735 A033667 A033923
Adjacent sequences: A130631 A130632 A130633 * A130635 A130636 A130637
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KEYWORD
| easy,nonn,base
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AUTHOR
| Paolo P. Lava & Giorgio Balzarotti (paoloplava(AT)gmail.com), Jun 19 2007, corrected Jun 22 2007
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