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 A121489 #14 Sep 15 2024 03:40:07 %S A121489 3,1,9,17,19,9,18,17,55,24,38,36,12,65,106,129,128,97,30,100,148,168, %T A121489 154,100,251,113,198,249,260,225,138,356,163,297,389,433,423,353,217, %U A121489 9,248,441,17,80,79,8,506,297,687,316,574,17,119,145,89,784,568,252,737 %N A121489 Diagonal of array A121490. %C A121489 Also, a(n) is the smallest positive integer such that n^3 + a(n) is a square. - _Bruno Berselli_, Jan 29 2013 %C A121489 For n = m^2, a(n) = 2*m^3 + 1; e.g., a(1) = 2*1^3 + 1 = 3, a(4) = 2*2^3 + 1 = 17, a(9) = 2*3^3 + 1 = 55; otherwise a(n) < 2*n^(3/2) + 1. - _Zak Seidov_, Mar 24 2013 %H A121489 Zak Seidov, <a href="/A121489/b121489.txt">Table of n, a(n) for n = 1..10000</a> %F A121489 a(n) = floor(n^(3/2) + 1)^2 - n^3. %e A121489 a(2) = floor(2^(3/2) + 1)^2 - 2^3 = 9 - 8 = 1. %K A121489 nonn,easy %O A121489 1,1 %A A121489 _Clark Kimberling_, Aug 02 2006