OFFSET
0,1
COMMENTS
This is the '13x+1' map. The 'Px+1 map': if x is divisible by any prime < P then divide out these primes one at a time starting with the smallest; otherwise multiply x by P and add 1.
LINKS
Eric Weisstein's World of Mathematics, Collatz problem
Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,0,0,0,0,0,0,0,1).
FORMULA
For n>15, a(n) = a(n-15). [Harvey P. Dale, May 02 2011]
EXAMPLE
73 -> 19*73+1 = 950, 950 = 2*5^2*19 -> 950/2 = 475, etc.
MATHEMATICA
nxt[n_]:=Which[Divisible[n, 2], n/2, Divisible[n, 3], n/3, Divisible[n, 5], n/5, Divisible[n, 7], n/7, Divisible[n, 11], n/11, True, 13n+1]; NestList[nxt, 73, 60] (* Harvey P. Dale, May 02 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Murad A. AlDamen (Divisibility(AT)yahoo.com), Oct 17 2000
STATUS
approved