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A281374 Coefficients in q-expansion of E_2^2, where E_2 is the Eisenstein series shown in A006352. 11
1, -48, 432, 3264, 9456, 21600, 39744, 66432, 105840, 147984, 220320, 281664, 393792, 475104, 646272, 743040, 980592, 1091232, 1432944, 1536960, 1965600, 2118144, 2649024, 2761344, 3516480, 3557040, 4433184, 4594560, 5575296, 5603040, 6998400, 6864384, 8407152, 8494848, 10085472, 9918720, 12319152 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..1000

MAPLE

with(numtheory); M:=100;

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

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

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

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

series(e2^2, q, M+1);

seriestolist(%);

MATHEMATICA

terms = 37;

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

E2[x]^2 + O[x]^terms // CoefficientList[#, x]& (* Jean-Fran├žois Alcover, Feb 23 2018 *)

CROSSREFS

Cf. A006352.

Sequence in context: A232917 A172201 A249293 * A190416 A231342 A192828

Adjacent sequences:  A281371 A281372 A281373 * A281375 A281376 A281377

KEYWORD

sign

AUTHOR

N. J. A. Sloane, Feb 05 2017

STATUS

approved

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Last modified November 24 19:02 EST 2020. Contains 338616 sequences. (Running on oeis4.)