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

1,4

Comments

Colors may be permuted without changing the necklace structure.

Links

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

Formula

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

Crossrefs

Cf. A056292, A306888, A327396, A328130.

Sequence in context: A303631 A358603 A076584 * A154343 A049969 A088634

Adjacent sequences: A309670 A309671 A309672 * A309674 A309675 A309676

Keyword

nonn

Author

Andrew Howroyd, Oct 05 2019

Extensions

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

Status

approved