OFFSET
0,2
COMMENTS
The corresponding denominators are 5^n.
LINKS
Hugo Pfoertner, Table of n, a(n) for n = 0..300
Hugo Pfoertner Plot of asinh(A370192(n)) vs asinh(A370191(n)), using Plot 2.
Index entries for linear recurrences with constant coefficients, signature (8,-20).
FORMULA
From Stefano Spezia, Feb 17 2024: (Start)
G.f.: -2*x/(1 - 8*x + 20*x^2).
E.g.f.: -exp(4*x)*sin(2*x). (End)
EXAMPLE
n (5/(1 + i/2))^n
A370191(n) a(n)
0 1 +0 *i
1 4 -2 *i
2 12 -16 *i
3 16 -88 *i
4 -112 -384 *i
5 -1216 -1312 *i
6 -7488 -2816 *i
7 -35584 +3712 *i
8 -134912 +86016 *i
MATHEMATICA
LinearRecurrence[{8, -20}, {0, -2}, 26]
PROG
(PARI) a370192(n) = numerator(imag(1/(1+I/2)^n))
CROSSREFS
KEYWORD
sign,frac,easy
AUTHOR
Hugo Pfoertner, Feb 17 2024
STATUS
approved