OFFSET
0,3
COMMENTS
This sequence is related to a greedily and recursively defined sequence (see links). - Sela Fried, Aug 30 2024
LINKS
Sela Fried, On integer sequence A128135, 2024.
Simon Plouffe, Illustration. [broken link]
Index entries for linear recurrences with constant coefficients, signature (0,4,0,-4).
FORMULA
G.f.: x*(1 + 4*x + 2*x^2)/(1 - 2*x^2)^2. - Ilya Gutkovskiy, Feb 24 2017
a(n) = n*A016116(n). - Michel Marcus, Feb 17 2018
Sum{n>=1} 1/a(n) = sqrt(2)*arcsinh(1) + log(2)/2. - Amiram Eldar, Sep 15 2024
MAPLE
seq(n*2^(floor(n/2)), n=1..120);
MATHEMATICA
Table[n*2^Floor[n/2], {n, 0, 100}] (* Wesley Ivan Hurt, Dec 12 2013 *)
LinearRecurrence[{0, 4, 0, -4}, {0, 1, 4, 6}, 50] (* Harvey P. Dale, Aug 27 2022 *)
PROG
(PARI) a(n) = n*2^(n\2); \\ Michel Marcus, Feb 17 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Simon Plouffe, Nov 19 2007
EXTENSIONS
More terms from Michel Marcus, Feb 17 2018
STATUS
approved