A037281 Number of iterations of transformation in A037280 needed to reach 1 or a prime, or -1 if no such number exists.
0, 0, 0, 1, 0, 1, 0, 1, 1, 2, 0
Offset: 1
Crossrefs
Cf. A037279.
Programs
-
Maple
with(numtheory):ds:=proc(s) local j: RETURN(add(s[j]*10^(j-1),j=1..nops(s))):end: a:=proc(n) options remember: local d,i,l,m: if n<3 then RETURN(1) else if not isprime(n) then d:=divisors(n): l:=nops(d): m:=ds([seq(op(convert(d[l-i+1],base,10)),i=2..l-1)]): RETURN(m/piecewise(m mod 2=1,1,2^(ifactors(m)[2][1][2]))) else RETURN(n) fi fi: end; for n from 1 to 11 do m:=n: for i from 0 while(not isprime(m) and m<>1) do m:=a(m) od: printf("%d, ",i) od: # C. Ronaldo
Extensions
Corrected by C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 29 2004
Comments