A279626 Number of palindromes over an alphabet of size 4 of length 2n+1 having no (3/2)+ powers.

4, 12, 24, 48, 120, 240, 480, 1104, 2448, 5376, 12048, 27456, 61704, 140664

Offset

0,1

Comments

A (3/2)+ power is a word of the form xx', where x' is a prefix of x and |x'| > |x|/2. Every odd length (2n+1) is guaranteed to have at least one such palindrome.

Links

Table of n, a(n) for n=0..13.

Example

For n = 2 the possibilities are {01210, 01310, 02120, 02320, 03130, 03230} and their images under permutations of the alphabet.

Crossrefs

Cf. A279611, A279625.

Sequence in context: A132477 A102651 A102652 * A238607 A143270 A037338

Adjacent sequences: A279623 A279624 A279625 * A279627 A279628 A279629

Keyword

nonn

Author

Jeffrey Shallit, Dec 16 2016

Status

approved