A050431 Length of longest palindromic subword of (n base 3).

1, 1, 1, 2, 1, 1, 1, 2, 2, 3, 1, 2, 3, 2, 1, 3, 2, 2, 1, 3, 1, 2, 3, 2, 2, 3, 3, 4, 2, 3, 3, 3, 3, 1, 2, 2, 3, 2, 3, 4, 3, 2, 3, 2, 2, 1, 3, 3, 3, 3, 2, 4, 3, 3, 2, 4, 3, 2, 1, 3, 3, 3, 2, 3, 1, 2, 3, 4, 3, 3, 3, 2, 2, 3, 2, 2, 3, 3, 3, 4, 4, 5, 3, 4, 4, 4, 3, 2, 2, 3

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A050430, A050432, A050433.

Programs

Maple

LPS:= proc(L) local nL, n, i;
  nL:= nops(L);
  for n from nL to 1 by -1 do
    for i from 1 to nL-n+1 do
      if L[i..i+n-1] = ListTools:-Reverse(L[i..i+n-1]) then return n fi
  od od:
end proc:
seq(LPS(convert(n, base, 3)), n=1..100); # Robert Israel, Dec 17 2020

Formula

a(n) <= min(a(3*n), a(3*n+1), a(3*n+2)). [Reinhard Zumkeller, Jul 31 2011]