A067422 Seventh column of triangle A067417.

1, 9, 189, 3969, 83349, 1750329, 36756909, 771895089, 16209796869, 340405734249, 7148520419229, 150118928803809, 3152497504879989, 66202447602479769, 1390251399652075149, 29195279392693578129

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..700

Index entries for linear recurrences with constant coefficients, signature (21).

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

Adjacent sequences: A067419 A067420 A067421 * A067423 A067424 A067425

Keyword

nonn,easy

Author

Wolfdieter Lang, Jan 25 2002

Status

approved