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 A086144 #14 Jun 11 2019 06:59:51
%S A086144 1,0,1,2,3,4,5,4,3,2,1,2,3,4,3,4,5,6,5,6,5,4,5,6,5,4,3,2,3,2,1,2,3,2,
%T A086144 3,4,5,6,7,6,7,6,7,8,7,6,5,6,7,6,7,8,9,10,9,10,9,8,7,8,9,8,9,8,7,6,7,
%U A086144 8,9,8,9,10,11,10,9,10,11,10,9,8,9,10,11,10,11,10,11,12,13,14
%N A086144 a(n) = 2*A071640(n) - n.
%C A086144 It is conjectured that A071640(n)/n -> 1/2. - _Benoit Cloitre_
%C A086144 a(6671) < 0. - _Peter Luschny_, Oct 05 2011
%p A086144 A086144 := proc(n) option remember; if n=1 then 1 else
%p A086144 if combinat[numbpart](n) mod 2 = 1 then 1 else -1 fi;
%p A086144 % + A086144(n-1) fi end: seq(A086144(i),i=1..90); # _Peter Luschny_, Oct 05 2011
%t A086144 a071640[n_] := Sum[Mod[PartitionsP[i], 2], {i, 1, n}];
%t A086144 a[n_] := 2 a071640[n] - n;
%t A086144 Array[a, 100] (* _Jean-François Alcover_, Jun 11 2019 *)
%o A086144 (PARI) a(n) = my(x='x+O('x^(n+1)), p = 1/eta(x)); sum(i=1, n, (1-(-1)^(polcoeff(p, i)))) - n; \\ _Michel Marcus_, Jun 11 2019
%Y A086144 Cf. A071640, A040051, A000041, A087177.
%K A086144 sign
%O A086144 1,4
%A A086144 _Benoit Cloitre_, Sep 06 2003
%E A086144 Erroneous data for n>55 replaced, keyword sign added by _Peter Luschny_, Oct 05 2011