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Coefficients in q-expansion of E_2^3, where E_2 is the Eisenstein series shown in A006352.
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%I #12 Feb 23 2018 03:40:30

%S 1,-72,1512,-3744,-95544,-473904,-1538784,-3947328,-8597880,-16987176,

%T -30607632,-52030944,-83972448,-129500784,-194056128,-279446976,

%U -397468152,-544155408,-743106744,-978896160,-1296984528,-1654458624,-2139055776,-2661349824,-3370243680,-4106376504,-5113466064

%N Coefficients in q-expansion of E_2^3, where E_2 is the Eisenstein series shown in A006352.

%H Seiichi Manyama, <a href="/A282018/b282018.txt">Table of n, a(n) for n = 0..1000</a>

%p with(numtheory); M:=100;

%p E := proc(k) local n, t1; global M;

%p t1 := 1-(2*k/bernoulli(k))*add(sigma[k-1](n)*q^n, n=1..M+1);

%p series(t1, q, M+1); end;

%p e2:=E(2); e4:=E(4); e6:=E(6);

%p series(e2^3,q,M+1);

%p seriestolist(%);

%t terms = 27;

%t E2[x_] = 1 - 24*Sum[k*x^k/(1 - x^k), {k, 1, terms}];

%t E2[x]^3 + O[x]^terms // CoefficientList[#, x]& (* _Jean-François Alcover_, Feb 23 2018 *)

%Y Cf. A006352.

%K sign

%O 0,2

%A _N. J. A. Sloane_, Feb 05 2017