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 A330827 #27 Jan 14 2020 00:54:07 %S A330827 1,1,1,1,1,1,3,1,1,1,1,3,1,3,1,5,3,3,5,3,5,3,3,1,3,1,1,1,1,3,1,3,3,5, %T A330827 3,5,3,5,5,5,7,5,7,7,5,9,7,7,11,7,9,7,7,7,11,9,13,5,9,5,15,7,9,7,7,7, %U A330827 7,7,5,5,5,3,5,3,5,3,3,1,3,1,1,1,1,3,1,3 %N A330827 a(n) is the numbers of ways to write 2*n = u + v where the ternary representations of u and of v have the same number of digits d for d = 0..2. %C A330827 In other words, a(n) is the number of ways to write 2*n as the sum of two ternary anagrams. %C A330827 Leading zeros are ignored. %C A330827 Two ternary anagrams have necessarily the same parity, hence an odd number cannot be the sum of two ternary anagrams. %H A330827 Rémy Sigrist, <a href="/A330827/b330827.txt">Table of n, a(n) for n = 0..19683</a> %H A330827 Rémy Sigrist, <a href="/A330827/a330827.gp.txt">PARI program for A330827</a> %H A330827 Rémy Sigrist, <a href="/A330827/a330827.png">Scatterplot of (x, y) such that 0 <= x, y <= 3^7 and x and y are ternary anagrams</a> (a(n) corresponds to the number of pixels (x, y) such that x+y = n) %e A330827 For n = 6: %e A330827 - we can write 12 as u + v in the following ways: %e A330827 u v ter(u) ter(v) %e A330827 - - ------ ------ %e A330827 5 7 12 21 %e A330827 6 6 20 20 %e A330827 7 5 21 12 %e A330827 - hence a(6) = 3. %o A330827 (PARI) See Links section. %Y A330827 Cf. A331216 (binary analog), A331218 (decimal analog). %K A330827 nonn,base %O A330827 0,7 %A A330827 _Rémy Sigrist_, Jan 12 2020