A029968 Palindromic in bases 13 and 10.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 222, 313, 353, 444, 575, 666, 797, 1111, 6776, 8778, 24542, 25452, 26362, 56265, 311113, 2377732, 2713172, 2832382, 2906092, 8864688, 10122101, 13055031, 20244202, 20944902, 23177132, 23877832

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Links

• Robert G. Wilson v, Table of n, a(n) for n = 1..76
• P. De Geest, Palindromic numbers beyond base 10

Crossrefs

Cf. A007632, A007633, A029961, A029962, A029963, A029964, A029804, A029965, A029966, A029967, A029969, A029970, A029731, A097855, A099165.

Programs

Mathematica

NextPalindrome[n_] := Block[{l = Floor[ Log[10, n] + 1], idn = IntegerDigits[n]}, If[ Union[idn] == {9}, Return[n + 2], If[l < 2, Return[n + 1], If[ FromDigits[ Reverse[ Take[idn, Ceiling[l/2]] ]] FromDigits[ Take[idn, -Ceiling[l/2]]], FromDigits[ Join[ Take[idn, Ceiling[l/2]], Reverse[ Take[idn, Floor[l/2]] ]]], idfhn = FromDigits[ Take[idn, Ceiling[l/2]]] + 1; idp = FromDigits[ Join[ IntegerDigits[idfhn], Drop[ Reverse[ IntegerDigits[idfhn]], Mod[l, 2]] ]]] ]]]; palQ[n_Integer, base_Integer] := Block[{idn = IntegerDigits[n, base]}, idn == Reverse[idn]]; l = {0}; a = 0; Do[a = NextPalindrome[a]; If[ palQ[a, 13], AppendTo[l, a]], {n, 100000}]; l (* Robert G. Wilson v, Sep 03 2004 *)
Select[Range[0, 10^5],
PalindromeQ[#] && # == IntegerReverse[#, 13] &] (* Robert Price, Nov 09 2019 *)

Python

from gmpy2 import digits
def palQ(n,b): # check if n is a palindrome in base b
    s = digits(n,b)
    return s == s[::-1]
def palQgen10(l): # generator of palindromes in base 10 of length <= 2*l
    if l > 0:
        yield 0
        for x in range(1,l+1):
            for y in range(10**(x-1),10**x):
                s = str(y)
                yield int(s+s[-2::-1])
            for y in range(10**(x-1),10**x):
                s = str(y)
                yield int(s+s[::-1])
A029968_list = [n for n in palQgen10(9) if palQ(n,13)]
# Chai Wah Wu, Dec 01 2014