A362109 Arises from the enumeration of cycle-alternating permutations.

1, 1, 2, 5, 17, 78, 461, 3417, 31134, 340217, 4365673, 64840274, 1101675849, 21181863649, 456577039642, 10949181225821, 290211071487473, 8451563567148662, 268994949663621813, 9313237898346027545, 349298002471856701110, 14138014197758841573105

Offset

0,3

Links

Table of n, a(n) for n=0..21.

Bishal Deb and Alan D. Sokal, Continued fractions for cycle-alternating permutations, arXiv:2304.06545 [math.CO], 2023. See (1.10).

Mathematica

Rest@CoefficientList[Fold[#2/(1-#1)&, O[t], Reverse@Join[{1, 1}, Riffle[Range[10]^2, 1]]], t] (* Andrei Zabolotskii, Jul 12 2025 *)

Crossrefs

Sequence in context: A199164 A184509 A020096 * A187245 A361243 A302194

Adjacent sequences: A362106 A362107 A362108 * A362110 A362111 A362112

Keyword

nonn

Author

N. J. A. Sloane, Apr 14 2023

Extensions

Terms a(11) onwards from Andrei Zabolotskii, Jul 12 2025

Status

approved