A371966 Largest number reachable starting from 1 and taking n steps either doubling or doubling+reversing.
1, 2, 4, 8, 61, 221, 442, 884, 8671, 24371, 60721, 244121, 881371, 2898371, 8692591, 48826601, 97653202, 484336211, 968672422, 6847550561, 24334620331, 68473110671, 247696944631, 884738088671, 2892570042961, 8872433043671, 44817108207511, 89634216415022, 486415512459511
Offset: 0
Examples
a(4) = 61 by the path 1, 2, 4, 8, 61.
Links
- Michael S. Branicky, Table of n, a(n) for n = 0..34
Programs
-
Python
from itertools import islice def reverse(n): return int(str(n)[::-1]) def agen(): # generator of terms reach = {1} while True: yield max(reach) newreach = set() for q in reach: newreach.update([2*q, reverse(2*q)]) reach = newreach print(list(islice(agen(), 28))) # Michael S. Branicky, Apr 14 2024
Formula
a(n) <= 20^n and a(n+1) <= 20*a(n).
Comments