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A373336 Expansion of Sum_{k>=1} x^k / (1 + x^k + x^(2*k) + x^(3*k) + x^(4*k) + x^(5*k) + x^(6*k)).

%I A373336 #13 Jun 01 2024 12:04:15
%S A373336 1,0,1,0,1,0,1,1,0,0,1,0,1,0,2,0,1,-1,1,0,1,1,0,1,1,0,0,0,2,0,1,0,1,0,
%T A373336 1,0,0,0,1,1,1,0,2,0,1,-1,1,0,1,1,0,0,1,-1,1,1,2,0,1,0,1,0,0,1,0,1,1,
%U A373336 0,0,0,2,0,1,-1,2,0,1,1,0,0,0,0,1,0,2,0,2,1,1,-1,1,0,0,0,1,0,1,0,1,0,1,-1,1,1,2
%N A373336 Expansion of Sum_{k>=1} x^k / (1 + x^k + x^(2*k) + x^(3*k) + x^(4*k) + x^(5*k) + x^(6*k)).
%H A373336 Seiichi Manyama, <a href="/A373336/b373336.txt">Table of n, a(n) for n = 1..10000</a>
%F A373336 G.f.: Sum_{k>=1} x^k * (1 - x^k) / (1 - x^(7*k)).
%F A373336 a(n) = A279061(n) - A363795(n).
%o A373336 (PARI) my(N=110, x='x+O('x^N)); Vec(sum(k=1, N, x^k*(1-x^k)/(1-x^(7*k))))
%o A373336 (PARI) a(n) = sumdiv(n, d, (d%7==1)-(d%7==2));
%Y A373336 Cf. A002324, A048272, A373335.
%Y A373336 Cf. A279061, A363795.
%K A373336 sign,easy
%O A373336 1,15
%A A373336 _Seiichi Manyama_, Jun 01 2024