A309673 Number of n-bead necklace structures using a maximum of four different colored beads and no adjacent beads having the same color.

0, 1, 1, 3, 2, 9, 13, 41, 94, 257, 671, 1881, 5110, 14301, 39871, 112281, 316520, 897297, 2548819, 7265383, 20754748, 59437181, 170549237, 490338539, 1412147684, 4073528481, 11767897903, 34042917197, 98606864030, 285960106473, 830206177801, 2412787265021

Offset: 1

Author

Andrew Howroyd, Oct 05 2019

Keywords

• nonn

Comments

Colors may be permuted without changing the necklace structure.

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A056292, A306888, A327396, A328130.

Formula

a(n) = Sum_{k=1..4} A327396(n, k).

Extensions

Terms a(24) and beyond from Andrew Howroyd, Oct 10 2019