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A074601
a(n) = 2^n + 6^n.
4
2, 8, 40, 224, 1312, 7808, 46720, 280064, 1679872, 10078208, 60467200, 362799104, 2176786432, 13060702208, 78364180480, 470185017344, 2821109972992, 16926659575808, 101559956930560, 609359740534784, 3656158441111552
OFFSET
0,1
LINKS
Wei Chen, Enumeration of Set Partitions Refined by Crossing and Nesting Numbers, MS Thesis, Department of Mathematics. Simon Fraser University, Fall 2014. Table 5.2, r=2.
FORMULA
a(n) = 6*a(n-1) - 2^n = 8*a(n-1) - 12*a(n-2).
From Mohammad K. Azarian, Jan 02 2009: (Start)
G.f.: 1/(1-2*x) + 1/(1-6*x).
E.g.f.: e^(2*x) + e^(6*x). (End)
MATHEMATICA
Table[2^n + 6^n, {n, 0, 22}]
PROG
(Magma) [2^n + 6^n: n in [0..35]]; // Vincenzo Librandi, Apr 30 2011
KEYWORD
easy,nonn
AUTHOR
Robert G. Wilson v, Aug 25 2002
STATUS
approved