A093123 Third binomial transform of Fibonacci(3n-1) (A015448).
1, 4, 20, 120, 800, 5600, 40000, 288000, 2080000, 15040000, 108800000, 787200000, 5696000000, 41216000000, 298240000000, 2158080000000, 15616000000000, 112998400000000, 817664000000000, 5916672000000000, 42813440000000000
Offset: 0
Links
- Index entries for linear recurrences with constant coefficients, signature (10, -20).
Formula
G.f.: (1-6x)/(1-10x+20x^2).
a(n) = (5-sqrt(5))*(5+sqrt(5))^n/10 + (5+sqrt(5))*(5-sqrt(5))^n/10.
a(n) = 2^n*A093129(n).