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A127847
a(n)=4^C(n,2)*(4^n-1)/3.
1
0, 1, 20, 1344, 348160, 357564416, 1465657589760, 24017731997138944, 1574098141758535761920, 412645105639632468417970176, 432690992231222540584116394393600, 1814838857553600260569028862094736359424, 30447948962887853884238295543591323273401466880
OFFSET
0,3
COMMENTS
-a(n) is the Hankel transform of A127846, the series reversion of x/(1+5x+4x^2). Note that (4^n-1)/3 has g.f. x/(1-5x+4x^2).
MATHEMATICA
Table[4^Binomial[n, 2] (4^n-1)/3, {n, 0, 20}] (* Harvey P. Dale, Aug 29 2015 *)
CROSSREFS
Sequence in context: A005982 A229476 A177597 * A363512 A193309 A177601
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Feb 02 2007
EXTENSIONS
More terms from Harvey P. Dale, Aug 29 2015
STATUS
approved