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A370966
a(n) = number of max-closed 2 X 2 X n relations.
1
1, 14, 122, 898, 6086, 39394, 248102, 1536178, 9409046, 57227074, 346467782, 2091269458, 12597590006, 75785795554, 455516874662, 2736312874738, 16430733386966, 98635853704834, 592021022116742, 3552949991056018, 21320996155647926, 127939164097754914, 767687740219762022
OFFSET
0,2
LINKS
Don Knuth, Parades and poly-Bernoulli bijections, Mar 31 2024. See (19.14) and (19.16).
Filip Stappers, Problems concerning parades and poly-Bernoulli numbers, 2024. See Problem 10.
FORMULA
From Filip Stappers, Aug 19 2024: (Start)
a(n) = 35/6*6^n - 6*4^n + 2/3*3^n + 1/2*2^n.
G.f.: (1-z)*(1-8*z^2) / ((1-6*z)*(1-4*z)*(1-3*z)*(1-2*z)). (End)
E.g.f.: exp(2*x)*(3 + 4*exp(x) - 36*exp(2*x) + 35*exp(4*x)). - Stefano Spezia, Aug 20 2024
CROSSREFS
Sequence in context: A206635 A163942 A206628 * A235710 A239544 A167567
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Apr 04 2024
EXTENSIONS
a(7)-a(9) from Michael S. Branicky, Apr 07 2024
a(10) from Michael S. Branicky, Apr 08 2024
a(11) from Michael S. Branicky, Apr 22 2024
More terms from Filip Stappers, Aug 14 2024
a(0)=1 prepended by Filip Stappers, Aug 19 2024
STATUS
approved