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 A226982 #16 Feb 09 2018 03:26:32 %S A226982 1,0,0,0,0,0,0,0,1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,4,4,5,5,5,5,5,5,6,6, %T A226982 7,7,7,7,8,8,8,8,8,8,9,9,9,9,10,10,11,11,11,11,12,12,13,13,13,13,13, %U A226982 13,14,14,15,15,15 %N A226982 a(n) = ceiling(n/2) - primepi(n). %C A226982 The number of partitions of 2n into exactly two parts such that the smaller part is an odd composite integer, n > 1. %C A226982 Sequence decreases by 1 when n is an even prime and increases by 1 when n is an odd composite. - _Wesley Ivan Hurt_, Dec 27 2013 %H A226982 <a href="/index/Par#part">Index entries for sequences related to partitions</a> %F A226982 a(n) = floor((n+1)/2) - pi(n) = A004526(n+1) - A000720(n). %F A226982 a(n) = n - A004526(n) - A000720(n). - _Wesley Ivan Hurt_, Dec 27 2013 %e A226982 a(18) =2. 2*18=38 has two partitions into exactly two odd parts with smallest part composite: (27,9) and (21,15). - _Wesley Ivan Hurt_, Dec 27 2013 %p A226982 seq(ceil(n/2)-numtheory[pi](n),n=1..100); %Y A226982 Cf. A000720, A004526, A002375, A141100. %K A226982 nonn,easy %O A226982 1,15 %A A226982 _Wesley Ivan Hurt_, Jun 25 2013