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 A117580 #6 Nov 29 2017 02:14:51
%S A117580 1,9,25,27,49,81,125,169,225,343,361,441,729,729,841,1331,1369,1521,
%T A117580 2197,2025
%N A117580 A cubic quadratic sequence arranged so that the modulo-3 equals one cubic sequence is just ahead of the quadratic sequence (called here the Maestro sequence).
%C A117580 Arranged so that they are near the Magic numbers (nuclear shell filling numbers): called Maestro as they have to be conducted like an orcestra to get them to behave this way.
%F A117580 g[n_] := (n - Floor[n/3])^3 /; Mod[n, 3] - 1 == 0 g[n_] := (2*n - 1)^2 /; (n < 4) g[n_] := (2*n - 1)^2 /; (n > 13) && (n < 17) g[n_] := (2*n - 3)^2 /; (n > 4) && (n < 13) g[n_] := (2*n + 3)^2 /; (n >= 17) && (n < 19) g[n_] := (2*n + 5)^2 /; (n >= 18) a(n) = g[n]
%t A117580 g[n_] := (n - Floor[n/3])^3 /; Mod[n, 3] - 1 == 0 g[n_] := (2*n - 1)^2 /; (n < 4) g[n_] := (2*n - 1)^2 /; (n > 13) && (n < 17) g[n_] := (2*n - 3)^2 /; (n > 4) && (n < 13) g[n_] := (2*n + 3)^2 /; (n >= 17) && (n < 19) g[n_] := (2*n + 5)^2 /; (n >= 18) a=Table[g[n], {n, 1, 20}]
%Y A117580 Cf. A018226.
%K A117580 nonn,uned
%O A117580 0,2
%A A117580 _Roger L. Bagula_, Apr 08 2006