OFFSET
0,2
COMMENTS
a(n) mod 9 is periodic: repeat 0, 4, 2, 3, 7, 5, 6, 1, 8.
b(n) = a(n) - n = 0, 3, 18, 99, 516, 2565, 12294,... = A215149(2n)/2.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (10,-33,40,-16).
FORMULA
EXAMPLE
a(0)=0*(2+1/2)=0, a(1)=1*(2+2)=4, a(2)=2*(2+8)=20, a(3)=3*(2+32)=102, a(4)=4*(2+128)=520, a(5)=5*(2+512)=2570.
MATHEMATICA
Table[(n (2 + 2^(2 n - 1))), {n, 0, 40}] (* Vincenzo Librandi, Sep 20 2013 *)
PROG
(PARI) a(n) = n*(2+2^(2*n-1)); \\ Michel Marcus, Sep 16 2013
(Magma) [n*(2 + 2^(2*n - 1)): n in [0..30]]; // Vincenzo Librandi, Sep 20 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, Sep 15 2013
EXTENSIONS
Better definition by Michel Marcus.
More terms from Vincenzo Librandi, Sep 20 2013
STATUS
approved