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A047639 Expansion of (Product_{j>=1} (1-(-x)^j) - 1)^14 in powers of x.

%I A047639 #20 Sep 07 2023 02:22:26
%S A047639 1,-14,91,-364,987,-1820,1897,754,-8008,18928,-26845,19460,15015,
%T A047639 -76272,141065,-163072,90727,99386,-368277,602616,-643734,358190,
%U A047639 274547,-1101100,1801086,-1982330,1344525,148316,-2163590,4032756,-4938843,4216576
%N A047639 Expansion of (Product_{j>=1} (1-(-x)^j) - 1)^14 in powers of x.
%H A047639 Alois P. Heinz, <a href="/A047639/b047639.txt">Table of n, a(n) for n = 14..10000</a>
%H A047639 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 A047639 H. Gupta, <a href="/A001482/a001482.pdf">On the coefficients of the powers of Dedekind's modular form</a> (annotated and scanned copy)
%F A047639 a(n) = [x^n]( QPochhammer(-x) - 1 )^14. - _G. C. Greubel_, Sep 07 2023
%p A047639 g:= proc(n) option remember; `if`(n=0, 1, add(add([-d, d, -2*d, d]
%p A047639       [1+irem(d, 4)], d=numtheory[divisors](j))*g(n-j), j=1..n)/n)
%p A047639     end:
%p A047639 b:= proc(n, k) option remember; `if`(k=0, 1, `if`(k=1, `if`(n=0, 0, g(n)),
%p A047639       (q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
%p A047639     end:
%p A047639 a:= n-> b(n, 14):
%p A047639 seq(a(n), n=14..45);  # _Alois P. Heinz_, Feb 07 2021
%t A047639 nmax=45; CoefficientList[Series[(Product[(1-(-x)^j), {j,nmax}] - 1)^14, {x,0,nmax}], x]//Drop[#, 14] & (* _Ilya Gutkovskiy_, Feb 07 2021 *)
%t A047639 With[{k=14}, Drop[CoefficientList[Series[(QPochhammer[-x] -1)^k, {x,0, 75}], x], k]] (* _G. C. Greubel_, Sep 07 2023 *)
%o A047639 (Magma)
%o A047639 m:=80;
%o A047639 R<x>:=PowerSeriesRing(Integers(), m);
%o A047639 Coefficients(R!( ((&*[1-(-x)^j: j in [1..m+2]]) -1)^(14) )); // _G. C. Greubel_, Sep 07 2023
%o A047639 (SageMath)
%o A047639 from sage.modular.etaproducts import qexp_eta
%o A047639 m=75; k=14;
%o A047639 def f(k,x): return (-1 + qexp_eta(QQ[['q']], m+2).subs(q=-x) )^k
%o A047639 def A047639_list(prec):
%o A047639     P.<x> = PowerSeriesRing(QQ, prec)
%o A047639     return P( f(k,x) ).list()
%o A047639 a=A047639_list(m); a[k:] # _G. C. Greubel_, Sep 07 2023
%o A047639 (PARI) my(x='x+O('x^40)); Vec((eta(-x)-1)^14) \\ _Joerg Arndt_, Sep 07 2023
%Y A047639 Cf. A001482 - A001488, A001490, A047638, A047640 - A047649, A047654, A047655, A341243.
%K A047639 sign
%O A047639 14,2
%A A047639 _N. J. A. Sloane_
%E A047639 Definition and offset edited by _Ilya Gutkovskiy_, Feb 07 2021