This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A257853 #16 Nov 13 2024 23:02:09 %S A257853 0,1,8,27,3,34,89,174,24,127,272,465,81,298,575,918,192,565,1016,1551, %T A257853 375,946,1613,2382,648,1459,2384,62,1029,2122,3347,263,1536,2953,4520, %U A257853 566,2187,3970,5921,989,3000,5191,7568,1550,3993,6634,9479,2267,5184,8317 %N A257853 a(n) = 2*n^3 - floor(2^(1/3)*n)^3. %C A257853 Is there a simple expression for a nontrivial lower bound for a(n)? %e A257853 a(4) = 2*4^3 - floor(2^(1/3)*4)^3 = 2*64 - 5^3 = 3. %e A257853 a(5) = 2*5^3 - floor(2^(1/3)*5)^3 = 2*125 - 6^3 = 34. %t A257853 Table[2 n^3 - Floor[2^(1/3) n]^3, {n, 0, 60}] (* _Vincenzo Librandi_, May 29 2015 *) %o A257853 (PARI) f(n,e=3,b=2)=n^e*b-floor(sqrtn(b,e)*n)^e %o A257853 (Magma) [2*n^3 - Floor(2^(1/3)*n)^3: n in [0..50]]; // _Vincenzo Librandi_, May 29 2015 %Y A257853 Cf. A087056 (analog for squares), A257854, A257855 (4th & 5th power). %K A257853 nonn,easy %O A257853 0,3 %A A257853 _M. F. Hasler_, May 28 2015