OFFSET
1,3
LINKS
Nathan Fox, Table of n, a(n) for n = 1..7832
N. Bradley Fox et al., Elated Numbers, arXiv:2409.09863 [math.NT], 2024.
EXAMPLE
21 is the 4th elated number and iterating the map A376270 yields 10 then 1, so a(4)=2.
PROG
(Python)
from itertools import count, islice
def f(n): return (d:=list(map(int, str(n))))[0] * sum(di*di for di in d)
def ok_count(n):
if n == 1: return True, 0
traj, c = {n}, 0
while (n:=f(n)) not in traj: traj.add(n); c += 1
return 1 in traj, c
def agen(): # generator of terms
for n in count(1):
elated, iterations = ok_count(n)
if elated: yield iterations
print(list(islice(agen(), 90))) # Michael S. Branicky, Oct 16 2024
CROSSREFS
KEYWORD
nonn,base
AUTHOR
N. Bradley Fox, Nathan Fox, Helen Grundman, Rachel Lynn, Changningphaabi Namoijam, Mary Vanderschoot, Oct 15 2024
STATUS
approved