A059138 A hierarchical sequence (S(W3{2,2}cc) - see A059126).

18, 90, 270, 666, 1494, 3186, 6606, 13482, 27270, 54882, 110142, 220698, 441846, 884178, 1768878, 3538314, 7077222, 14155074, 28310814, 56622330, 113245398, 226491570, 452983950, 905968746, 1811938374, 3623877666, 7247756286, 14495513562, 28991028150

Offset: 0

Author

Jonas Wallgren, Jan 19 2001

Keywords

• nonn

Links

• Jonas Wallgren, Hierarchical sequences
• Index entries for linear recurrences with constant coefficients, signature (4, -5, 2).

Crossrefs

Cf. A059126.

Formula

Conjectures from Colin Barker, Oct 07 2015: (Start)

a(n) = 18*(-5 + 3*2^(1+n) - 2*n) = 18*A050488(n+1).

a(n) = 4*a(n-1) - 5*a(n-2) + 2*a(n-3) for n>2.

G.f.: -18*(x+1) / ((x-1)^2*(2*x-1)).

(End)

Extensions

More terms from Sean A. Irvine, Sep 13 2022