A129985 Multiplicative persistence of the prime numbers.

0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 3, 2, 3, 1, 2, 1, 2, 3, 2, 3, 3, 1, 1, 1, 1, 1, 2, 1, 2, 3, 3, 1, 3, 2, 2, 2, 3, 1, 1, 3, 3, 2, 1, 2, 3, 3, 2, 3, 1, 2, 2, 3, 2, 2, 4, 2, 3, 3, 1, 1, 1, 2, 1, 3, 3, 2, 3, 3, 3, 3, 4, 3, 3, 4, 1, 1, 3, 1, 2, 3, 2, 3, 3, 2, 2, 3, 4, 3, 3, 3, 3, 1, 1, 2, 2, 2

Offset

0,10

Links

Table of n, a(n) for n=0..99.

Example

229 -> 2*2*9=36 -> 3*6=18 -> 1*8=8 -> persistence = 3

Maple

P:=proc(n) local i, k, w, ok, cont, x; for i from 1 by 1 to n do k:=ithprime(i); w:=1; ok:=1; x:=k; 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

Sequence in context: A209315 A352218 A174713 * A085243 A265745 A092243

Adjacent sequences: A129982 A129983 A129984 * A129986 A129987 A129988

Keyword

easy,nonn,base

Author

Paolo P. Lava and Giorgio Balzarotti, Jun 14 2007

Status

approved