A071272 Palindromes in A066492.

1, 2, 3, 4, 5, 6, 7, 8, 9, 101, 111, 121, 131, 141, 151, 161, 171, 181, 202, 212, 222, 232, 242, 252, 262, 272, 303, 313, 323, 333, 343, 353, 363, 404, 414, 424, 434, 444, 454, 505, 515, 525, 535, 545, 606, 616, 626, 636, 707, 717, 727, 808, 818, 909, 10001

Offset

1,2

Comments

Conjecture: m is a term if and only if 1<=m<=9 or m is a palindrome of odd length 2k+1 such that the sum of the k-th and (k+1)-th decimal digits is less than or equal to 9. - Chai Wah Wu, May 30 2026

Also palindromes p such that 11*p is a palindrome with an even number of digits. - David A. Corneth, May 30 2026

Links

David A. Corneth, Table of n, a(n) for n = 1..10000

Prog

(Python)
from itertools import count, islice
def A071272_gen():
    for n in count(1):
        m = (n*10**len(s:=str(n))+int(s[::-1]))//11
        if (t:=str(m))==t[::-1]:
            yield m
A071272_list = list(islice(A071272_gen(), 40)) # Chai Wah Wu, May 30 2026
(PARI) is(n) = {if(!ispal(n), return(0)); ispal(11*n) && #digits(11*n) % 2 == 0}
ispal(n) = n == fromdigits(Vecrev(digits(n))) \\ David A. Corneth, May 30 2026

Crossrefs

Cf. A056524, A066492.

Sequence in context: A240237 A056142 A056525 * A083851 A071275 A050783

Adjacent sequences: A071269 A071270 A071271 * A071273 A071274 A071275

Keyword

nonn,easy,base,changed

Author

Amarnath Murthy, Jun 07 2002

Extensions

More terms from Sean A. Irvine, Jul 07 2024

Status

approved