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%I M4371 N1835 #25 Sep 04 2023 06:08:21
%S 1,-7,21,-35,28,21,-105,181,-189,77,140,-385,546,-511,252,203,-693,
%T 1029,-1092,798,-203,-581,1281,-1708,1687,-1232,413,602,-1485,2233,
%U -2366,2009,-1099,14,1099,-2072,2667,-2807,2254,-1477,0,1057,-2346,2744,-3017,2457
%N Expansion of (Product_{j>=1} (1-(-x)^j) - 1)^7 in powers of x.
%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Alois P. Heinz, <a href="/A001485/b001485.txt">Table of n, a(n) for n = 7..10000</a>
%H H. Gupta, <a href="https://doi.org/10.1112/jlms/s1-39.1.433">On the coefficients of the powers of Dedekind's modular form</a>, J. London Math. Soc., 39 (1964), 433-440.
%H H. Gupta, <a href="/A001482/a001482.pdf">On the coefficients of the powers of Dedekind's modular form</a> (annotated and scanned copy)
%F a(n) = [x^n] ( QPochhammer(-x) - 1 )^7. - _G. C. Greubel_, Sep 04 2023
%p g:= proc(n) option remember; `if`(n=0, 1, add(add([-d, d, -2*d, d]
%p [1+irem(d, 4)], d=numtheory[divisors](j))*g(n-j), j=1..n)/n)
%p end:
%p b:= proc(n, k) option remember; `if`(k=0, 1, `if`(k=1, `if`(n=0, 0, g(n)),
%p (q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
%p end:
%p a:= n-> b(n, 7):
%p seq(a(n), n=7..52); # _Alois P. Heinz_, Feb 07 2021
%t nmax = 52; CoefficientList[Series[(Product[(1 - (-x)^j), {j, 1, nmax}] - 1)^7, {x, 0, nmax}], x] // Drop[#, 7] & (* _Ilya Gutkovskiy_, Feb 07 2021 *)
%t Drop[CoefficientList[Series[(QPochhammer[-x] -1)^7, {x,0,102}], x], 7] (* _G. C. Greubel_, Sep 04 2023 *)
%o (Magma)
%o m:=102;
%o R<x>:=PowerSeriesRing(Integers(), m);
%o Coefficients(R!( ((&*[1-(-x)^j: j in [1..m+2]]) -1)^7 )); // _G. C. Greubel_, Sep 04 2023
%o (SageMath)
%o m=100; k=7;
%o def f(k,x): return (-1 + product( (1+x^j)*(1-x^(2*j))/(1+x^(2*j)) for j in range(1,m+2) ) )^k
%o def A001485_list(prec):
%o P.<x> = PowerSeriesRing(QQ, prec)
%o return P( f(k,x) ).list()
%o a=A001485_list(m); a[k:] # _G. C. Greubel_, Sep 04 2023
%o (PARI) my(N=70,x='x+O('x^N)); Vec((eta(-x)-1)^7) \\ _Joerg Arndt_, Sep 04 2023
%Y Cf. A001482, A001483, A001484, A001486, A001487, A001488, A047638 - A047649, A047654, A047655, A341243.
%K sign
%O 7,2
%A _N. J. A. Sloane_
%E Definition and offset edited by _Ilya Gutkovskiy_, Feb 07 2021
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