A046237 Numbers whose cube is palindromic in base 7.

0, 1, 2, 4, 8, 16, 50, 100, 200, 344, 688, 1376, 2402, 4804, 9608, 16808, 33616, 67232, 117650, 235300, 470600, 823544, 1647088, 3294176, 5764802, 11529604, 23059208, 40353608, 80707216, 161414432, 282475250, 564950500, 1129901000, 1977326744, 3954653488, 7909306976

Offset: 1

Author

Patrick De Geest, May 15 1998

Keywords

• nonn
• base

Comments

Contains triples with base-7 digits 10^k1, 20^k2, 40^k4 for k >= 1, where ^ denotes repeated concatenation. - Michael S. Branicky, Aug 02 2022

Links

• Patrick De Geest, World!Of Numbers, Palindromic cubes in bases 2 to 17.

Crossrefs

Cf. A046238.

Programs

PARI

isok(k) = my(d=digits(k^3, 7)); Vecrev(d) == d; \\ Michel Marcus, Aug 02 2022

Python

from itertools import count, islice
from sympy.ntheory import is_palindromic as ispal
def agen(start=0): yield from (k for k in count(start) if ispal(k**3, 7))
print(list(islice(agen(), 22))) # Michael S. Branicky, Aug 02 2022

Extensions

a(30)-a(36) from Michael S. Branicky, Aug 03 2022