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A019266
Cycle class sequence c(2n) (the number of true cycles of length 2n in which a certain node is included) for square lattice.
1
1, 0, 4, 12, 56, 280, 1488, 8232, 47008, 274824, 1636520, 9890584, 60510480, 374019776, 2332131872, 14651535840, 92653845120, 589317728376, 3767523372432, 24196006128592, 156030800105840, 1009911004804296, 6558631830442384, 42723991459518368, 279091277437885920
OFFSET
0,3
LINKS
G. Thimm and W. E. Klee, Zeolite cycle sequences, Zeolites, 19, pp. 422-424, 1997.
FORMULA
a(n) = A010566(n) / 2 = 2 * n * A002931(n) for n > 0. - Andrey Zabolotskiy, Jul 26 2022
MATHEMATICA
(Length@FindCycle[{NearestNeighborGraph[Tuples[Range[2 # + 4], 2], {All, 1.}], {#+2, #+2}}, {2 #}, All]) & /@ Range[11] (* Gabriel B. Apolinario, Jan 07 2017 *)
CROSSREFS
Sequence in context: A164575 A124004 A243785 * A009114 A144012 A197924
KEYWORD
nonn
AUTHOR
Georg Thimm (mgeorg(AT)ntu.edu.sg)
EXTENSIONS
a(11) from Gabriel B. Apolinario, Jan 07 2017
a(12)-a(18) from Aleksandr D. Krotov, Jan 07 2018
a(19)-a(20) from Aleksandr D. Krotov, Mar 22 2019
Terms a(21) and beyond added by Andrey Zabolotskiy, Jul 26 2022, using A002931
STATUS
approved