A225373 a(n) = 1 + Sum_{i=0..floor(n/2)} phi(n-2*i).

1, 2, 2, 4, 4, 8, 6, 14, 10, 20, 14, 30, 18, 42, 24, 50, 32, 66, 38, 84, 46, 96, 56, 118, 64, 138, 76, 156, 88, 184, 96, 214, 112, 234, 128, 258, 140, 294, 158, 318, 174, 358, 186, 400, 206, 424, 228, 470, 244, 512, 264, 544, 288, 596, 306, 636, 330, 672, 358, 730

Offset

0,2

Comments

Number of Sturmian palindromes of length n.

Links

Table of n, a(n) for n=0..59.

Michelangelo Bucci, Alessandro De Luca, Amy Glen and Luca Q. Zamboni, A connection between palindromic and factor complexity using return words, arXiv:0802.1332 [math.CO], 2008.

Formula

a(n) = A106481(n) + 1. - Filip Zaludek, Dec 16 2016

Maple

with(numtheory);
f:=n->1+add(phi(n-2*i), i=0..floor(n/2));
[seq(f(n), n=0..100)];

Mathematica

Table[1 + Sum[EulerPhi[n - 2 i], {i, 0, Floor[n/2]}], {n, 0, 59}] (* Michael De Vlieger, Dec 17 2016 *)

Crossrefs

Cf. A000010.

Sequence in context: A330807 A008330 A191234 * A138219 A279405 A100835

Adjacent sequences: A225370 A225371 A225372 * A225374 A225375 A225376

Keyword

nonn

Author

N. J. A. Sloane, May 08 2013

Extensions

Name corrected by Michael De Vlieger, Dec 17 2016

Status

approved