A333512 Numbers nontrivially palindromic in exactly three consecutive number bases.

1654123, 4564873, 1687837537501, 195766180573603

Offset

1,1

Comments

Numbers which are strictly non-palindromic up to a set of k=3 consecutive number bases. It is conjectured that such a sequence for k>=4 is empty. For a special case of k=0, we have the sequence A016038.

A subsequence of A279093. Notice that a(1),a(2),a(3),a(4) are all of the form (b^3 + 3 b^2 + 5 b + 2)/2 where b=2k+6, for k=71,101,7497,36575. Not all terms are necessarily of this form. (See comments in A279093, containing a total of 9 known such forms that generate numbers palindromic in three consecutive number bases.)

For every n, a(n) should be a prime number.

Links

Table of n, a(n) for n=1..4.

Example

N = 1654123 is a palindrome when written in three consecutive number bases b = 148,149,150 and is not a palindrome in any other nontrivial number bases 2 <= b <= N-2. The three palindromic representations are: 1654123 = (75,76,75)_148 = (74,75,74)_149 =  (73,77,73)_150. Hence, this number is a term of the sequence.

Crossrefs

Cf. A279092, A279093 (consecutive palindromes), A016038 (strictly non-palindromic numbers), A060792 (palindromes in bases 2 and 3).

Sequence in context: A144127 A072922 A204762 * A061127 A183798 A158957

Adjacent sequences: A333509 A333510 A333511 * A333513 A333514 A333515

Keyword

nonn,hard,more

Author

Matej Veselovac, Mar 25 2020

Status

approved