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A295860
a(n) = a(n-1) + 3*a(n-2) -2*a(n-3) - 2*a(n-4), where a(0) = -2, a(1) = 1, a(2) = 0, a(3) = 1.
5
-2, 1, 0, 1, 3, 4, 11, 15, 34, 49, 99, 148, 279, 427, 770, 1197, 2095, 3292, 5643, 8935, 15090, 24025, 40139, 64164, 106351, 170515, 280962, 451477, 740631, 1192108, 1949123, 3141231, 5123122, 8264353, 13453011, 21717364, 35301447, 57018811, 92582402
OFFSET
0,1
COMMENTS
a(n)/a(n-1) -> (1 + sqrt(5))/2 = golden ratio (A001622), so that a( ) has the growth rate of the Fibonacci numbers (A000045).
FORMULA
G.f.: (-2 + 3 x + 5 x^2 - 6 x^3)/(1 - x - 3 x^2 + 2 x^3 + 2 x^4).
a(n) = -A016116(n+1) + 4*A000045(n) - A000045(n+1). - Robert Israel, Jan 12 2018
MAPLE
f:= n -> - 2^floor((n+1)/2) + 4*combinat:-fibonacci(n) - combinat:-fibonacci(n+1):
map(f, [$0..30]); # Robert Israel, Jan 12 2018
MATHEMATICA
LinearRecurrence[{1, 3, -2, -2}, {-2, 1, 0, 1}, 100]
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Clark Kimberling, Jan 07 2018
STATUS
approved