A067422 Seventh column of triangle A067417.

1, 9, 189, 3969, 83349, 1750329, 36756909, 771895089, 16209796869, 340405734249, 7148520419229, 150118928803809, 3152497504879989, 66202447602479769, 1390251399652075149, 29195279392693578129, 613100867246565140709, 12875118212177867954889

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).

From Elmo R. Oliveira, Jun 07 2026: (Start)

a(n) = 21*a(n-1) for n > 1.

E.g.f.: (4 + 3*exp(21*x))/7. (End)

Mathematica

Join[{1}, 9*21^Range[0, 20]] (* Paolo Xausa, Jun 23 2026 *)

Prog

(Magma) [Ceiling(9*(3*7)^(n-1)): n in [0..20]]; // Vincenzo Librandi, Oct 02 2011

Crossrefs

Cf. A067417.

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,changed

Author

Wolfdieter Lang, Jan 25 2002

Status

approved