0,7

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

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

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);

Cf. A031346, A130543.

Sequence in context: A145998 A009832 A016445 this_sequence A007739 A031424 A013942

Adjacent sequences: A130541 A130542 A130543 this_sequence A130545 A130546 A130547

easy,nonn

Paolo P. Lava & Giorgio Balzarotti (ppl(AT)spl.at), Jun 04 2007