OFFSET
0,2
COMMENTS
The interest of this sequence mainly lies in the peculiarities of its array of successive differences, which begins:
1, 2, 4, 8, 16, 23, 37, 56, 94, ...
1, 2, 4, 8, 7, 14, 19, 38, 58, ...
1, 2, 4, -1, 7, 5, 19, 20, 40, ...
1, 2, -5, 8, -2, 14, 1, 20, 13, ...
1, -7, 13, -10, 16, -13, 19, -7, 31, ...
-8, 20, -23, 26, -29, 32, -26, 38, -23, ...
28, -43, 49, -55, 61, -58, 64, -61, 67, ...
The main diagonal is A000079 (powers of 2).
The first upper subdiagonal is A254076.
The second upper subdiagonal (4, 8, 7, 14, 19, 38, ...) is not in the OEIS.
The third upper subdiagonal is A185346 (2^n-9).
Every row, once computed mod 9, is 6-periodic, repeating (1, 2, 4, 8, 7, 5) (A153130).
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,1,-1,1,1).
FORMULA
G.f.: (1+x+x^2+3*x^3+5*x^4) / (1-x-x^2+x^3-x^4-x^5).
a(n) = (9/2)*fibonacci(n) + (-1)^n - sqrt(3)*sin(n*Pi/3).
a(n) ~ (9/2)*fibonacci(n).
MATHEMATICA
LinearRecurrence[{1, 1, -1, 1, 1}, {1, 2, 4, 8, 16}, 40]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jean-François Alcover and Paul Curtz, Oct 29 2017
STATUS
approved