A359222 - OEIS

A359222

Number of steps to reach 0 from A359221(n) (Starting numbers that reach a new record high value during iteration by the map x->A359194(x)).

0, 1, 2, 11, 80, 7572, 664475, 3180929, 120796790, 556068798, 1246707529, 87037147316

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

COMMENTS

a(12) found by Tom Duff (26 Dec 2022).

It is unknown whether all starting numbers reach 0.

LINKS

EXAMPLE

a(4) is the step count from the starting number A359221(4) = 3: (3, 6, 13, 24, 55, 90, 241, 300, 123, 142, 85, 0) -- 11 steps, hence a(4) = 11.

PROG

(Python)

from itertools import count, islice

def f(n): return 1 if n == 0 else (m:=3*n)^((1 << m.bit_length())-1)

def itersmax(n):

i, fi, m = 0, n, n

while fi != 0: i, fi, m = i+1, f(fi), max(m, fi)

return i, m

def agen(): # generator of terms

record = -1

for m in count(0):

v, mx = itersmax(m)

if mx > record:

yield v # use m to obtain starting numbers

record = mx

print(list(islice(agen(), 8))) # Michael S. Branicky, Dec 29 2022

CROSSREFS

Step counts of A359221.

KEYWORD

nonn,base,more,hard

AUTHOR

STATUS

approved