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 A339399 #37 Jan 09 2022 00:16:27 %S A339399 1,1,1,2,1,3,2,2,1,4,2,3,1,5,2,4,3,3,1,6,2,5,3,4,1,7,2,6,3,5,4,4,1,8, %T A339399 2,7,3,6,4,5,1,9,2,8,3,7,4,6,5,5,1,10,2,9,3,8,4,7,5,6,1,11,2,10,3,9,4, %U A339399 8,5,7,6,6,1,12,2,11,3,10,4,9,5,8,6,7,1,13,2,12,3,11 %N A339399 Pairwise listing of the partitions of k into two parts (s,t), with 0 < s <= t ordered by increasing values of s and where k = 2,3,... . %C A339399 a(n-1) and a(n) are the lesser and greater of a twin prime pair if and only if a(n) = a(n-1) + 2 where a(n-1) and a(n) are prime. %H A339399 <a href="/index/Par#part">Index entries for sequences related to partitions</a> %F A339399 a(n) = (1+(-1)^n)*(1+floor(sqrt(2*n-1-(-1)^n)))/2-((2*n+1-(-1)^n)/2-2 *Sum_{k=1..floor(sqrt(2*n-2-(-1)^n)-1)} floor((k+1)/2))*(-1)^n/2. %F A339399 a(n) = A339443(A103889(n)). - _Wesley Ivan Hurt_, May 09 2021 %e A339399 [1,9] %e A339399 [1,7] [1,8] [2,8] %e A339399 [1,5] [1,6] [2,6] [2,7] [3,7] %e A339399 [1,3] [1,4] [2,4] [2,5] [3,5] [3,6] [4,6] %e A339399 [1,1] [1,2] [2,2] [2,3] [3,3] [3,4] [4,4] [4,5] [5,5] %e A339399 k 2 3 4 5 6 7 8 9 10 %e A339399 -------------------------------------------------------------------------- %e A339399 k Nondecreasing partitions of k %e A339399 -------------------------------------------------------------------------- %e A339399 2 1,1 %e A339399 3 1,2 %e A339399 4 1,3,2,2 %e A339399 5 1,4,2,3 %e A339399 6 1,5,2,4,3,3 %e A339399 7 1,6,2,5,3,4 %e A339399 8 1,7,2,6,3,5,4,4 %e A339399 9 1,8,2,7,3,6,4,5 %e A339399 10 1,9,2,8,3,7,4,6,5,5 %e A339399 ... %t A339399 t[n_] := Flatten[Reverse /@ IntegerPartitions[n, {2}]]; Array[t, 14, 2] // Flatten (* _Amiram Eldar_, Dec 03 2020 *) %t A339399 Table[(1 + (-1)^n) (1 + Floor[Sqrt[2 n - 1 - (-1)^n]])/2 - ((2 n + 1 - (-1)^n)/2 - 2 Sum[Floor[(k + 1)/2], {k, -1 + Floor[Sqrt[2 n - 2 - (-1)^n]]}]) (-1)^n/2, {n, 100}] (* _Wesley Ivan Hurt_, Dec 04 2020 *) %o A339399 (PARI) row(n) = vector(n\2, i, [i, n-i]); %o A339399 tabf(nn) = for (n=2, nn, print(row(n))); \\ _Michel Marcus_, Dec 03 2020 %Y A339399 Cf. A103889, A339443. %Y A339399 Bisections: A122197 (odd), A199474 (even). %K A339399 nonn,tabf %O A339399 1,4 %A A339399 _Wesley Ivan Hurt_, Dec 02 2020