OFFSET
1,1
EXAMPLE
25 -> 2^5 = 32 -> 3^2 = 9.
PROG
(Python)
def powertrain(n):
p, s = 1, str(n)
if len(s)%2 == 1: s += '1'
for b, e in zip(s[0::2], s[1::2]): p *= int(b)**int(e)
return p
def aupto(limit, target=0):
alst = []
for n in range(1, limit+1):
m, ptm = n, powertrain(n)
while m != ptm: m, ptm = ptm, powertrain(ptm)
if m == target: alst.append(n)
return alst
print(aupto(1191, target=9)) # Michael S. Branicky, Sep 25 2021
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Martin Renner, Jul 22 2019
STATUS
approved