A202337 Range of A062723.

1, 2, 6, 12, 36, 108, 324, 972, 2916, 8748, 26244, 78732, 236196, 708588, 2125764, 6377292, 19131876, 57395628, 172186884, 516560652, 1549681956, 4649045868, 13947137604, 41841412812, 125524238436, 376572715308, 1129718145924, 3389154437772, 10167463313316

Offset: 1

Author

Reinhard Zumkeller, Dec 17 2011

Keywords

• nonn

Comments

Subsequence of A000792.

Apparently a(n) = A052156(n - 1) for n >= 4. - Georg Fischer, Mar 26 2019

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (3).

Crossrefs

Cf. A000792, A003946, A027327, A025579, A052156, A062723.

Programs

Haskell

a202337 n = a202337_list !! (n-1)
a202337_list = f a062723_list where
   f (x:xs'@(x':xs)) = if x == x' then f xs' else x : f xs'

Formula

From Colin Barker, Mar 26 2019: (Start)

G.f.: x*(1 - x - 6*x^3) / (1 - 3*x).

a(n) = 4*3^(n-3) for n>3.

a(n) = 3*a(n-1) for n>4.

(End)