OFFSET
0,3
COMMENTS
Is there a simple expression for a nontrivial lower bound for a(n)?
EXAMPLE
a(5) = 2*5^4 - floor(2^(1/4)*5)^4 = 2*625 - 5^4 = 625.
a(6) = 2*6^4 - floor(2^(1/4)*6)^4 = 2*1296 - 7^4 = 191.
MATHEMATICA
Table[2 n^4 - Floor[2^(1/4) n]^4, {n, 0, 60}] (* Vincenzo Librandi, May 29 2015 *)
PROG
(PARI) f(n, e=4, b=2)=n^e*b-floor(sqrtn(b, e)*n)^e
(Magma) [2*n^4 - Floor(2^(1/4)*n)^4: n in [0..50]]; // Vincenzo Librandi, May 29 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
M. F. Hasler, May 28 2015
STATUS
approved