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A067422
Seventh column of triangle A067417.
4
1, 9, 189, 3969, 83349, 1750329, 36756909, 771895089, 16209796869, 340405734249, 7148520419229, 150118928803809, 3152497504879989, 66202447602479769, 1390251399652075149, 29195279392693578129
OFFSET
0,2
FORMULA
a(n) = A067417(n+6, 6).
a(n) = 9*(3*7)^(n-1), n >= 1, a(0)=1.
G.f.: (1-12*x)/(1-21*x).
PROG
(Magma) [Ceiling(9*(3*7)^(n-1)): n in [0..20]]; // Vincenzo Librandi, Oct 02 2011
CROSSREFS
Cf. A067421 (sixth column), A067423 (eighth column), A009965 (powers of 21).
Sequence in context: A196682 A124008 A033713 * A347855 A249932 A278751
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Jan 25 2002
STATUS
approved