OFFSET
0,3
COMMENTS
Is there a simple expression for a nontrivial lower bound for a(n)?
EXAMPLE
a(4) = 2*4^3 - floor(2^(1/3)*4)^3 = 2*64 - 5^3 = 3.
a(5) = 2*5^3 - floor(2^(1/3)*5)^3 = 2*125 - 6^3 = 34.
MATHEMATICA
Table[2 n^3 - Floor[2^(1/3) n]^3, {n, 0, 60}] (* Vincenzo Librandi, May 29 2015 *)
PROG
(PARI) f(n, e=3, b=2)=n^e*b-floor(sqrtn(b, e)*n)^e
(Magma) [2*n^3 - Floor(2^(1/3)*n)^3: n in [0..50]]; // Vincenzo Librandi, May 29 2015
CROSSREFS
KEYWORD
nonn,easy,changed
AUTHOR
M. F. Hasler, May 28 2015
STATUS
approved