OFFSET
1,4
FORMULA
a(n) = A006577(n) mod n.
EXAMPLE
For n = 3, which takes 7 steps to reach 1 in the Collatz (3x+1) problem: (10, 5, 16, 8, 4, 2, 1), 7 mod 3 = 1.
MATHEMATICA
Table[Mod[-1 + Length[NestWhileList[If[EvenQ@ #, #/2, 3 # + 1] &, n, # != 1 &]], n], {n, 72}] (* Michael De Vlieger, Jun 09 2017 *)
PROG
(Python)
def stepCount(x):
x = int(x)
steps = 0
while True:
if x == 1:
break
elif x % 2 == 0:
x = x/2
steps += 1
else:
x = x*3 + 1
steps += 1
return steps
n = 1
while True:
print(stepCount(n) % n)
n += 1
(PARI) a(n)=s=n; c=0; while(s>1, s=if(s%2, 3*s+1, s/2); c++); c % n; \\ Michel Marcus, Jun 10 2017
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Ryan Pythagoras Newton Critchlow, Jun 07 2017
STATUS
approved