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A000731 Expansion of Product (1 - x^k)^8 in powers of x.
(Formerly M4488 N1900)
11
1, -8, 20, 0, -70, 64, 56, 0, -125, -160, 308, 0, 110, 0, -520, 0, 57, 560, 0, 0, 182, -512, -880, 0, 1190, -448, 884, 0, 0, 0, -1400, 0, -1330, 1000, 1820, 0, -646, 1280, 0, 0, -1331, -2464, 380, 0, 1120, 0, 2576, 0, 0, -880, 1748, 0, -3850, 0, -3400, 0, 2703, 4160, -2500, 0, 3458 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Number 22 of the 74 eta-quotients listed in Table I of Martin 1996.

Denoted by g_4(q) in Cynk and Hulek in Remark 3.4 on page 12 as the unique level 9 form of weight 4.

This is a member of an infinite family of integer weight modular forms. g_1 = A033687, g_2 = A030206, g_3 = A130539, g_4 = A000731. - Michael Somos, Aug 24 2012

a(n)=0 if and only if A033687(n)=0 (see the Han-Ono paper). - Emeric Deutsch, May 16 2008

Cubic AGM theta functions: a(q) (see A004016), b(q) (A005928), c(q) (A005882).

REFERENCES

Newman, Morris; A table of the coefficients of the powers of $\eta(\tau)$. Nederl. Akad. Wetensch. Proc. Ser. A. 59 = Indag. Math. 18 (1956), 204-216.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=0..60.

M. Boylan, Exceptional congruences for the coefficients of certain eta-product newforms, J. Number Theory 98 (2003), no. 2, 377-389. MR1955423 (2003k:11071)

S. Cynk and K. Hulek, Construction and examples of higher-dimensional modular Calabi-Yau manifolds

S. R. Finch, Powers of Euler's q-Series, (arXiv:math.NT/0701251).

G.-N. Han and Ken Ono,Hook lengths and 3-cores

Y. Martin, Multiplicative eta-quotients, Trans. Amer. Math. Soc. 348 (1996), no. 12, 4825-4856, see page 4852 Table I.

Index entries for expansions of Product_{k >= 1} (1-x^k)^m

FORMULA

Expansion of q^(-1/3) * eta(q)^8 in powers of q.

Expansion of q^(-1/3) * b(q)^3 * c(q) / 3 in powers of q where b(), c() are cubic AGM theta functions. - Michael Somos, Nov 08 2006

Expansion of q^(-1) * b(q) * c(q)^3 / 27 in powers of q^3 where b(), c() are cubic AGM theta functions. - Michael Somos, Nov 08 2006

Euler transform of period 1 sequence [ -8, ...].

a(n) = b(3*n + 1) where b(n) is multiplicative and b(3^e) = 0^e, b(p^e) = (1 + (-1)^e)/2 * (-1)^(e/2) * p^(3*e/2) if p == 2 (mod 3), b(p^e) = b(p)*b(p^(e-1)) - b(p^(e-2))*p^3 if p == 1 (mod 3) where b(p) = (x^2 - 3*p)*x, 4*p = x^2 + 3*y^2, |x|<|y| and x == 2 (mod 3). - Michael Somos, Aug 23 2006

Given g.f. A(x), then B(x) = x * A(x^3) satisfies 0 = f(B(x), B(x^2), B(x^4)) where f(u, v, w) = v^3 - u * w * (u + 16 * w). - Michael Somos, Feb 19 2007

G.f. is a period 1 Fourier series which satisfies f(-1 / (9 t)) = 81 (t/i)^4 f(t) where q = exp(2 Pi i t). - Michael Somos, Sep 29 2011

G.f.: Product_{k>0} (1 - x^k)^8.

a(2*n) = A153728(n). - Michael Somos, Sep 29 2011

a(4*n + 1) = -8 * a(n). - Michael Somos, Dec 06 2004

a(4*n + 3) = a(16*n + 13) = 0. - Michael Somos, Oct 19 2005

A092342(n) = a(n) + 81*A033690(n-1). - Michael Somos, Aug 22 2007

Sum_{n>=0} a(n) * q^(3*n + 1) = (Sum_{i,j,k in Z} (i-j) * (j-k) * (k-i) * q^((i*i + j*j + k*k) / 2)) / 2 where 0 = i+j+k, i == 1 (mod 3), j == 2 (mod 3), and k == 0 (mod 3). - Michael Somos, Sep 22 2014

EXAMPLE

G.f. = 1 - 8*x + 20*x^2 - 70*x^3 + 64*x^4 + 56*x^5 - 125*x^6 - 160*x^7 + ...

G.f. = q - 8*q^4 + 20*q^7 - 70*q^13 + 64*q^16 + 56*q^19 - 125*q^25 - ...

MATHEMATICA

a[ n_] := SeriesCoefficient[ QPochhammer[ q]^8, {q, 0, n}]; (* Michael Somos, Sep 29 2011 *)

a[ n_] := SeriesCoefficient[ Product[ 1 - q^k, {k, n}]^8, {q, 0, n}]; (* Michael Somos, Dec 09 2013 *)

PROG

(PARI) {a(n) = if( n<0, 0, polcoeff( eta(x + x * O(x^n))^8, n))};

(PARI) {a(n) = local(A, p, e, x, y, a0, a1); if( n<0, 0, n = 3*n + 1; A = factor(n); prod( k=1, matsize(A)[1], if( p=A[k, 1], e = A[k, 2]; if( p==3, 0, if( p%3==2, if( e%2, 0, (-1)^(e/2) * p^(3*e/2)), forstep( y=sqrtint(4*p\3), sqrtint(p\3), -1, if( issquare( 4*p - 3*y^2, &x), if( x%3!=2, x=-x); break)); a0=1; a1 = y = x * (x^2 - 3*p); for( i=2, e, x = y*a1 - p^3*a0; a0=a1; a1=x); a1)))))}; /* Michael Somos, Aug 23 2006 */

(Sage) CuspForms( Gamma0(9), 4, prec=100).0; # Michael Somos, May 28 2013

(MAGMA) Basis( CuspForms( Gamma0(9), 4), 100) [1]; /* Michael Somos, Dec 09 2013 */

CROSSREFS

Cf. A033687, A033690, A092342, A153728.

Sequence in context: A029845 A124972 * A161969 A034433 A225912 A120081

Adjacent sequences:  A000728 A000729 A000730 * A000732 A000733 A000734

KEYWORD

sign

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Corrected by Charles R Greathouse IV, Sep 02 2009

STATUS

approved

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Last modified October 26 02:56 EDT 2014. Contains 248566 sequences.