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

1,3

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

Table of n, a(n) for n=1..36.

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

Prog

(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

Crossrefs

Cf. A046238.

Sequence in context: A027155 A129335 A264635 * A013084 A263535 A018681

Adjacent sequences: A046234 A046235 A046236 * A046238 A046239 A046240

Keyword

nonn,base

Author

Patrick De Geest, May 15 1998

Extensions

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

Status

approved