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

1,10

Comments

Continuation from a(12): -1, 0, 3, 4, 1, 0, -1, 0, -1, 1, 1, 0, -1, 1, 4, 2, -1, 0, -1, 0, 2, 1, -1, 3, -1, 0, 2, 1, -1, 0, -1, 0, -1, -1, 1, 0, -1, 1, -1, 1, -1, 0, 1, 2, -1, 2, 1, 0, -1; where all the -1's are conjectural. - Franklin T. Adams-Watters, Jul 28 2011

Links

Table of n, a(n) for n=1..11.

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

Crossrefs

Cf. A037279.

Sequence in context: A368006 A374061 A374276 * A143241 A308064 A258825

Adjacent sequences: A037278 A037279 A037280 * A037282 A037283 A037284

Keyword

nonn,base,more

Author

N. J. A. Sloane

Extensions

Corrected by C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 29 2004

Status

approved