A131838 Multiplicative persistence of Woodall numbers.

0, 0, 1, 2, 3, 3, 2, 1, 1, 1, 2, 2, 1, 2, 2, 1, 5, 2, 2, 1, 1, 8, 3, 1, 1, 1, 2, 2, 2, 2, 1, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 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

Offset

1,4

Comments

After the 111th term, all the numbers have some digits equal to zero, thus the persistence is equal to 1.

Links

Table of n, a(n) for n=1..105.

Example

Woodall number 159 --> 1*5*9=45 --> 4*5=20 --> 2*0=0 thus persistence is 3.

Maple

P:=proc(n) local i, k, w, ok, cont; for i from 1 by 1 to n do w:=1; k:=i*2^i-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(120);

Crossrefs

Cf. A003261, A131841.

Sequence in context: A307429 A261283 A123548 * A274885 A287732 A334223

Adjacent sequences: A131835 A131836 A131837 * A131839 A131840 A131841

Keyword

easy,nonn,base

Author

Paolo P. Lava and Giorgio Balzarotti, Jul 20 2007

Status

approved