login
A009421
Cubes, not ending in 0, formed by concatenating other cubes.
2
10648, 27818127, 1018108216, 11728027648, 27081081027, 216108018001, 216648648216, 1001801080216, 27008100810027, 125112533753375, 125180086413824, 216010800180001, 216064806480216, 216270112515625, 1000180010800216, 1728648081003375, 1812501158328125
OFFSET
1,1
LINKS
FORMULA
a(n) = A061341(n)^3. - Michel Marcus, Apr 23 2018
EXAMPLE
2272^3 = 1_1728_0_27_64_8.
PROG
(Python)
from sympy import integer_nthroot
def iscube(n): return integer_nthroot(n, 3)[1]
def ok3(n, c):
if n%10 == 9 or (c == 1 and n%10 == 0): return False
if c > 1 and iscube(n): return True
d = str(n)
for i in range(1, len(d)):
if iscube(int(d[:i])) and ok3(int(d[i:]), c+1): return True
return False
print([r**3 for r in range(122000) if ok3(r**3, 1)]) # Michael S. Branicky, Jul 11 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
R. Muller
EXTENSIONS
Name clarified by Tanya Khovanova, Jul 10 2021
STATUS
approved