A393015 - OEIS

%I #21 Feb 05 2026 14:00:28

%S 101,202,212,303,313,323,404,414,424,434,505,515,525,535,545,606,616,

%T 626,636,646,656,707,717,727,737,747,757,767,808,818,828,838,848,858,

%U 868,878,909,919,929,939,949,959,969,979,989,21012,31013,32023,32123,41014,42024,42124,43034

%N Palindromic canyon numbers.

%C Canyon numbers (A134970) that are also palindromes (A002113).

%C All terms have an odd number of digits.

%C Finite because A134970 is finite, with largest term a(1013) = 9876543210123456789.

%H Michael S. Branicky, <a href="/A393015/b393015.txt">Table of n, a(n) for n = 1..1013</a>

%e Illustration of 8720278 as a canyon palindrome:

%e   . . . . . . .

%e   8 . . . . . 8

%e   . 7 . . . 7 .

%e   . . . . . . .

%e   . . . . . . .

%e   . . . . . . .

%e   . . . . . . .

%e   . . 2 . 2 . .

%e   . . . . . . .

%e   . . . 0 . . .

%o (Python)

%o from itertools import chain, combinations as combs

%o downs = list(chain.from_iterable(combs("9876543210", r) for r in range(2, 11)))

%o afull = sorted(int("".join(D + D[-2::-1])) for D in downs)

%o print(afull[:53]) # _Michael S. Branicky_, Jan 31 2026

%Y Intersection of A002113 and A134970.

%Y Cf. A134971, A173070.

%K nonn,base,fini,full

%O 1,1

%A _Alexander Yutkin_, Jan 31 2026