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 A111335 #26 Sep 06 2024 22:24:52
%S A111335 1,1,1,0,0,1,1,0,-1,0,2,1,-1,-1,1,2,-1,-2,1,3,1,-3,-1,3,1,-3,-2,4,4,
%T A111335 -3,-4,3,5,-3,-7,2,9,0,-9,-1,10,3,-11,-5,12,8,-11,-10,10,12,-11,-15,
%U A111335 11,19,-7,-21,6,24,-5,-28,1,31,4,-33,-8,36,12,-38,-18,40,27,-40,-33,40,39,-40,-49,38,60,-34,-67,30,75,-25,-87,18,98
%N A111335 Let qf(a,q) = Product_{j>=0} (1 - a*q^j); g.f. is qf(q^3,q^4)/qf(q,q^4).
%H A111335 Alois P. Heinz, <a href="/A111335/b111335.txt">Table of n, a(n) for n = 0..1000</a>
%F A111335 Euler transform of period 4 sequence [1, 0, -1, 0, ...]. - _Michael Somos_, Nov 10 2005
%F A111335 G.f.: Product_{k>0} (1-x^(2k-1))^((-1)^k). - _Michael Somos_, Nov 11 2005
%F A111335 G.f.: exp( Sum_{k >= 1} 1/(k*(x^k + x^(-k))) ). - _Peter Bala_, Sep 28 2023
%p A111335 # Uses EulerTransform from A358369.
%p A111335 a := EulerTransform(BinaryRecurrenceSequence(0, -1)):
%p A111335 seq(a(n), n=0..86); # _Peter Luschny_, Nov 17 2022
%o A111335 (PARI) {a(n)=if(n<0, 0, polcoeff( prod(k=0,n\2, (1-x^(2*k+1))^(-(-1)^k), 1+x*O(x^n)), n))} /* _Michael Somos_, Nov 11 2005 */
%o A111335 (Sage) # uses[EulerTransform from A166861]
%o A111335 b = BinaryRecurrenceSequence(0, -1)
%o A111335 a = EulerTransform(b)
%o A111335 print([a(n) for n in range(87)]) # _Peter Luschny_, Nov 17 2022
%Y A111335 Cf. A111330.
%K A111335 sign,look
%O A111335 0,11
%A A111335 _N. J. A. Sloane_, Nov 09 2005