A029839 -id:A029839 - cp's OEIS frontend

A079006 Expansion of q^(-1/4) * (eta(q) * eta(q^4)^2 / eta(q^2)^3)^2 in powers of q.

1, -2, 5, -10, 18, -32, 55, -90, 144, -226, 346, -522, 777, -1138, 1648, -2362, 3348, -4704, 6554, -9056, 12425, -16932, 22922, -30848, 41282, -54946, 72768, -95914, 125842, -164402, 213901, -277204, 357904, -460448, 590330, -754368, 960948, -1220370

Offset: 0

Michael Somos, Dec 22 2002

Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).

The Lagrange series reversion of Sum_{n >= 1} a(n-1)*x^n is Sum_{n >= 1} A002103(n-1)*x^n. See the example in A002103. - Wolfdieter Lang, Jul 09 2016

			G.f. A(x) = 1 - 2*x + 5*x^2 - 10*x^3 + 18*x^4 - 32*x^5 + 55*x^6 - 90*x^7 + 144*x^8 + ...
G.f. B(q) = q * A(q^4) = q - 2*q^5 + 5*q^9 - 10*q^13 + 18*q^17 - 32*q^21 + 55*q^25 - 90*q^29 + ...

A. Cayley, A memoir on the transformation of elliptic functions, Collected Mathematical Papers. Vols. 1-13, Cambridge Univ. Press, London, 1889-1897, Vol. 9, p. 128.
N. J. Fine, Basic Hypergeometric Series and Applications, Amer. Math. Soc., 1988; Eq. (34.3).

Seiichi Manyama, Table of n, a(n) for n = 0..10000 (terms 0..1000 from G. C. Greubel)
A. Cayley, A memoir on the transformation of elliptic functions, Philosophical Transactions of the Royal Society of London (1874): 397-456; Collected Mathematical Papers. Vols. 1-13, Cambridge Univ. Press, London, 1889-1897, included in Vol. 9. [Annotated scan of pages 126-129]
H. R. P. Ferguson, D. E. Nielsen and G. Cook, A partition formula for the integer coefficients of the theta function nome, Math. Comp., 29 (1975), 851-855.
R. Fricke, Die elliptischen Funktionen und ihre Anwendungen, Dritter Teil, Springer-Verlag, 2012, eq. (8), p. 11 with eq. (2), p. 10.
Nicco, Conjectured identity of the product of two theta functions, Math Stackexchange, Sep 09 2015.
Michael Somos, Introduction to Ramanujan theta functions
Eric Weisstein's World of Mathematics, Ramanujan Theta Functions

Cf. A000700, A001936, A002103, A008441, A029839, A046897, A083365, A127391, A127392, A189925.

a[ n_] := SeriesCoefficient[ Product[(1 + x^(k + 1)) / (1 + x^k), {k, 1, n, 2}]^2, {x, 0, n}]; (* Michael Somos, Jul 08 2011 *)
a[ n_] := With[ {m = InverseEllipticNomeQ[ q]}, SeriesCoefficient[ (m / 16 / q)^(1/4), {q, 0, n}]]; (* Michael Somos, Jul 08 2011 *)
QP = QPochhammer; s = (QP[q]*(QP[q^4]^2/QP[q^2]^3))^2 + O[q]^40; CoefficientList[s, q] (* Jean-François Alcover, Nov 23 2015 *)
nmax = 50; CoefficientList[Series[Product[(1+x^(2*k))^4 / (1+x^k)^2, {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Jul 04 2016 *)
a[ n_] := SeriesCoefficient[ QPochhammer[ x^4]^2 / QPochhammer[ -x]^2, {x, 0, n}]; (* Michael Somos, Apr 19 2017 *)

{a(n) = my(N, A); if( n<0, 0, N = (sqrtint(16*n + 1) + 1)\2; A = contfracpnqn( matrix(2, N, i, j, if( i==1, if( j<2, 1 + O(x^(N^2 + N)), (x^(j-1) + x^(3*j - 3))^2), 1 - x^(4*j - 2)))); polcoeff( A[2,1] / A[1,1], 4*n))}; /* Michael Somos, Sep 01 2005 */

{a(n) = my(A, m); if( n<0, 0, A = 1 + O(x); m = 1; while( m<=n, m*=2; A = subst(A, x, x^2); A = sqrt(A / (1 + 4 * x*A^2))); polcoeff(A, n))};

{a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( (eta(x + A) * eta(x^4 + A)^2 / eta(x^2 + A)^3)^2, n))};

a(n) = (2/n)*Sum_{k=1..n} (-1)^k*A046897(k)*a(n-k). - Vladeta Jovovic, Dec 24 2002
Expansion of q^(-1/4) * (1/2) * k^(1/2) in powers of q, where k^2 is the parameter and q the Jacobi nome of elliptic functions.
Expansion of (1/(2*q)) * (1 - sqrt(k')) / (1 + sqrt(k')) in powers of q^4, where k'^2 is the complementary parameter and q the Jacobi nome of elliptic functions. See the Fricke reference.
Expansion of psi(x^2) / phi(x) = psi(x)^2 / phi(x)^2 = psi(x^2)^2 / psi(x)^2 = psi(-x)^2 / phi(-x^2)^2 = chi(-x)^2 / chi(-x^2)^4 = 1 / (chi(x)^2 * chi(-x^2)^2) = 1 / (chi(x)^4 * chi(-x)^2) = f(-x^4)^2 / f(x)^2 in powers of x where phi(), psi(), chi(), f() are Ramanujan theta functions.
Euler transform of period 4 sequence [-2, 4, -2, 0, ...].
G.f. A(x) satisfies A(x)^2 = A(x^2) / (1 + 4 * x * A(x^2)^2). - Michael Somos, Mar 19 2004
Given g.f. A(x), then B(q) = q * A(q^4) satisfies 0 = f(B(q), B(q^2)) where f(u, v) = u^2 * (1 + 4 * v^2) - v. - Michael Somos, Jul 09 2005
Given g.f. A(x), then B(q) = q * A(q^4) satisfies 0 = f(B(q), B(q^2), B(q^3), B(q^6)) where f(u1, u2, u3, u6) = u1*u3 * (u6 + u2)^2 - u2*u6. - Michael Somos, Jul 09 2005
G.f.: (Product_{k>0} (1 + x^(2*k)) / (1 + x^(2*k-1)))^2 = (Product_{k>0} (1 - x^(4*k)) / (1 - (-x)^k))^2.
Expansion of continued fraction 1 / (1 - x^2 + (x^1 + x^3)^2 / (1 - x^6 + (x^2 + x^6)^2 / (1 - x^10 + (x^3 + x^9)^2 / ...))) in powers of x^4. - Michael Somos, Sep 01 2005
Given g.f. A(x), then B(q) = 2 * q * A(q^4) satisfies 0 = f(B(q), B(q^3)) where f(u, v) = (1 - u^4) * (1 - v^4) - (1 - u*v)^4 . - Michael Somos, Jan 01 2006
G.f. is a period 1 Fourier series which satisfies f(-1 / (16 t)) = (1/2) g(t) where q = exp(2 Pi i t) and g() is g.f. for A189925.
Convolution inverse of A029839. Convolution square of A083365. a(n) = (-1)^n * A001936(n).
G.f.: 1/Q(0), where Q(k)= 1 - x^(k+1/2) + (x^((k+1)/4) + x^((3*k+3)/4))^2/Q(k+1); (continued fraction). - Sergei N. Gladkovskii, May 02 2013
a(n) ~ (-1)^n * exp(Pi*sqrt(n)) / (2^(7/2)*n^(3/4)). - Vaclav Kotesovec, Jul 04 2016
Given g.f. A(x), and B(x) is the g.f. for A008441, then A(x) = B(x^2) / B(x) and A(x) * A(x^2) * A(x^4) * ... = 1 / B(x). - Michael Somos, Apr 20 2017
Expansion of continued fraction 1 / (1 - x^1 + x^1*(1 + x^1)^2 / (1 - x^3 + x^2*(1 + x^2)^2 / (1 - x^5 + x^3*(1 + x^3)^2 / ...))) in powers of x^2. - Michael Somos, Apr 20 2017
a(n) = A208933(4*n+1) - A215348(4*n+1) (conjectured). - Thomas Baruchel, May 14 2018
A(x^4) = (1/(m*x)) * ( chi(x)^m - chi(-x)^m ) / ( chi(x)^m + chi(-x)^m ) at m = 2, where chi(x)  = Product_{i >= 0} (1 + x^(2*i+1)) is the g.f. of A000700. The formula gives generating functions related to A092869 when m = 1 and A001938 (also A093160) when m = 4. - Peter Bala, Sep 23 2023

A029838 Expansion of square root of q times normalized Hauptmodul for Gamma(4) in powers of q^8.

Original entry on oeis.org

1, 1, -1, 0, 1, 0, -1, -1, 2, 1, -2, -1, 2, 1, -3, -1, 4, 2, -5, -2, 5, 2, -6, -3, 8, 4, -9, -4, 10, 4, -12, -6, 15, 7, -17, -7, 19, 8, -22, -10, 26, 12, -30, -13, 33, 14, -38, -17, 45, 21, -51, -22, 56, 24, -64, -29, 74, 33, -83, -36, 92, 40, -104, -46, 119, 53, -133, -58, 147, 63, -165, -73, 187, 83, -208, -90, 229, 99, -256

Offset: 0

N. J. A. Sloane

sign

Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).

			G.f. = 1 + x - x^2 + x^4 - x^6 - x^7 + 2*x^8 + x^9 - 2*x^10 - x^11 + 2*x^12 + ...
G.f. = 1/q + q^7 - q^15 + q^31 - q^47 - q^55 + 2*q^63 + q^71 - 2*q^79 - q^87 + ...

B. C. Berndt, Ramanujan's Notebooks Part III, Springer-Verlag, see p. 221 Entry 1(i).

Seiichi Manyama, Table of n, a(n) for n = 0..10000
W. Duke, Continued fractions and modular functions, Bull. Amer. Math. Soc. 42 (2005), 137-162; see Eqs. (9.1),(9.3).
J. McKay and A. Sebbar, Fuchsian groups, automorphic functions and Schwarzians, Math. Ann. 318 (2000), no. 2, 255-275.
Michael Somos, Introduction to Ramanujan theta functions
Eric Weisstein's World of Mathematics, Ramanujan Theta Functions, q-Pochhammer Symbol

Cf. A029839, A082303, A083365.

a[ n_] := SeriesCoefficient[ QPochhammer[ -q, q^2] QPochhammer[ q^2, q^4], {q, 0, n}]; (* Michael Somos, Aug 20 2014 *)
a[ n_] := SeriesCoefficient[ QPochhammer[ -q, -q] / QPochhammer[ q^4, q^4], {q, 0, n}]; (* Michael Somos, Aug 20 2014 *)
a[ n_] := SeriesCoefficient[ q^(1/8) EllipticTheta[ 2, 0, q^(1/2)] / EllipticTheta[ 2, 0, q], {q, 0, n}]; (* Michael Somos, Aug 20 2014 *)
(QPochhammer[-x, x^2, 1/2] + O[x]^100)[[3]] (* Vladimir Reshetnikov, Nov 20 2016 *)

{a(n) = if( n<0, 0, polcoeff( prod( k=1, n, (1 + x^k)^(-(-1)^k), 1 + x * O(x^n)), n))};

{a(n) = my(A); if( n<0, 0, A = contfracpnqn( matrix(2, (sqrtint(8*n + 1) + 1)\2, i, j, if( i==1, x^(j-1), 1 + if( j>1, x^(j-1))))); polcoeff(A[1,1] / A[2,1] + x * O(x^n), n))}; /* Michael Somos, Mar 02 2006 */

{a(n) = my(A, m); if( n<0, 0, A = 1 + O(x); m=1; while( m<=n, m*=2; A = subst(A, x, x^2); A2 = subst(A, x, x^2); A = sqrt((A2 + 2  * x / A2) / A)); polcoeff(A, n))};

{a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^2 + A)^3 / eta(x + A) / eta(x^4 + A)^2, n))};

Expansion of f(x) / f(-x^4) = phi(x) / psi(x) = psi(x) / psi(x^2) = phi(-x^2) / psi(-x) = chi(x) * chi(-x^2) = chi^2(x) * chi(-x) = chi^2(-x^2) / chi(-x) = (phi(x) / psi(x^2))^(1/2) in powers of x where phi(), psi(), chi(), f() are Ramanujan theta functions.
Expansion of q^(1/8) * eta(q^2)^3 / (eta(q) * eta(q^4)^2) in powers of q.
Euler transform of period 4 sequence [ 1, -2, 1, 0, ...].
Given g.f. A(x), then B(q) = A(q^8) / q satisfies 0 = f(B(q), B(q^2)) where f(u, v) = 4 + v^4 - u^4*v^2. - Michael Somos, Mar 02 2006
Given g.f. A(x), then B(q) = A(q^8) / q satisfies 0 = f(B(q), B(q^3)) where f(u, v) = u^4 - v^4 - 4*u*v + u^3*v^3. - Michael Somos, Mar 02 2006
Given g.f. A(x), then B(q) = A(q^8) / q satisfies 0 = f(B(q), B(q^2), B(q^4)) where f(u, v, w) = 2 + w^2 - u^2*v*w. - Michael Somos, Mar 02 2006
Given g.f. A(x), then B(q) = A(q^8) / q satisfies 0 = f(B(q), B(q^2), B(q^3), B(q^6)) where f(u1, u2, u3, u6) = u2^2 + u6^2 - u1*u2*u3*u6. - Michael Somos, Mar 02 2006
G.f. A(x) satisfies A(x)^2 = (A(x^4) + 2*x / A(x^4)) / A(x^2). - Michael Somos, Mar 08 2004
G.f. A(x) satisfies A(x) = (A(x^2)^2+4*x/A(x^2)^2)^(1/4). - Joerg Arndt, Aug 06 2011
G.f.: Product_{k>0} (1 + x^(2*k - 1)) / (1 + x^(2*k)) = (Sum_{k>0} x^((k^2 - k)/2)) / (Sum_{k>0} x^(k^2 - k)).
G.f.: 1 + x / (1 + x + x^2 / (1 + x^2 + x^3 / (1 + x^3 + ...))).
A082303(n) = (-1)^n a(n). Convolution square is A029839. Convolution inverse is A083365.
G.f.: 2 - 2/(1+Q(0)), where Q(k)= 1 + x^(k+1) + x^(k+1)/Q(k+1); (continued fraction). - Sergei N. Gladkovskii, May 02 2013
G.f.: (-x; x^2){1/2}, where (a; q)_n is the q-Pochhammer symbol. - _Vladimir Reshetnikov, Nov 20 2016
a(0) = 1, a(n) = (1/n)*Sum_{k=1..n} A109506(k)*a(n-k) for n > 0. - Seiichi Manyama, Apr 14 2017
abs(a(n)) ~ sqrt(sqrt(2) + (-1)^n) * exp(Pi*sqrt(n)/2^(3/2)) / (4*n^(3/4)). - Vaclav Kotesovec, Feb 07 2023

A029841 McKay-Thompson series of class 8E for the Monster group.

Original entry on oeis.org

1, 4, 2, -8, -1, 20, -2, -40, 3, 72, 2, -128, -4, 220, -4, -360, 5, 576, 8, -904, -8, 1384, -10, -2088, 11, 3108, 12, -4552, -15, 6592, -18, -9448, 22, 13392, 26, -18816, -29, 26216, -34, -36224, 38, 49700, 42, -67728, -51, 91688

Offset: 0

N. J. A. Sloane

A Hauptmodul for Gamma'_0(8).

Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).

			G.f. = 1 + 4*x + 2*x^2 - 8*x^3 - x^4 + 20*x^5 - 2*x^6 - 40*x^7 + 3*x^8 + ...
T8E = 1/q + 4*q + 2*q^3 - 8*q^5 - q^7 + 20*q^9 - 2*q^11 - 40*q^13 + 3*x^15 + ...

A. Cayley, An Elementary Treatise on Elliptic Functions, 2nd ed, 1895, p. 380, Section 488.

Seiichi Manyama, Table of n, a(n) for n = 0..10000 (terms 0..1000 from T. D. Noe)
J. H. Conway and S. P. Norton, Monstrous Moonshine, Bull. Lond. Math. Soc. 11 (1979) 308-339. See page 336.
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
J. McKay and A. Sebbar, Fuchsian groups, automorphic functions and Schwarzians, Math. Ann., 318 (2000), 255-275.
J. McKay and H. Strauss, The q-series of monstrous moonshine and the decomposition of the head characters, Comm. Algebra 18 (1990), no. 1, 253-278.
Michael Somos, Introduction to Ramanujan theta functions
Eric Weisstein's World of Mathematics, Ramanujan Theta Functions
Index entries for McKay-Thompson series for Monster simple group

Cf. A001938, A029839, A029845, A079006, A112143.

a[ n_] := With[ {m = InverseEllipticNomeQ @ q}, SeriesCoefficient[ 4 / Sqrt[m], {q, 0, n - 1/2}]]; (* Michael Somos, Aug 01 2011 *)
a[ n_] := With[ {m = InverseEllipticNomeQ @ q}, SeriesCoefficient[ 2 (1 + Sqrt[m]) / m^(1/4), {q, 0, n/2 - 1/4}]]; (* Michael Somos, Aug 01 2011 *)
a[ n_] := SeriesCoefficient[ (QPochhammer[ x^2]^3 / (QPochhammer[ x] QPochhammer[x^4]^2))^4, {x, 0, n}]; (* Michael Somos, Aug 20 2014 *)

{a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( (eta(x^2 + A)^3 / (eta(x + A) * eta(x^4 + A))^2)^4, n))};

{a(n) = my(A, m); if( n<0, 0, A = 1 + O(x); m=1; while( m<=n, m*=2; A = subst(A, x, x^2); A = (4*x + A) / sqrt(A)); polcoeff(A, n))};

G.f.: ( Product_{k>0} (1 + q^(2*k - 1)) / (1 + q^(2*k)) )^4.
Expansion of q^(1/4) * (1 + k) / k^(1/2) in powers of q^(1/2) where q is Jacobi's nome and k is the elliptic modulus. - Michael Somos, Aug 01 2011
Expansion of q^(1/2) * 4 / k in powers of q where q is Jacobi's nome and k is the elliptic modulus. - Michael Somos, Aug 01 2011 and Feb 28 2012
Expansion of (phi(x) / psi(x))^4 in powers of x where phi(), psi() are Ramanujan theta functions.
Expansion of q^(1/2) * (eta(q^2)^3 / (eta(q) * eta(q^4)^2))^4 in powers of q. - Michael Somos, Aug 01 2011
Euler transform of period 4 sequence [4, -8, 4, 0, ...]. - Michael Somos, Mar 18 2004
Given g.f. A(x), then B(q) = A(q^2) / q satisfies 0 = f(B(q), B(q^2)) where f(u, v) = 16 + 8*v + v^2 - u^2*v. - Michael Somos, Mar 18 2004
G.f. A(q) satisfies A(q) = sqrt(A(q^2))+4*q/sqrt(A(q^2)). - Joerg Arndt, Aug 06 2011
A112143(n) = (-1)^n * a(n). a(2*n) = A029839(n). a(2*n + 1) = 4 * A079006(n). - Michael Somos, Mar 27 2004.
Convolution inverse of A001938. Convolution square of A029839. Convolution square is A029845.

A029840 Expansion of Product_{m>=1} ((1+q^(2m-1))/(1+q^(2m)))^3.

Original entry on oeis.org

1, 3, 0, -5, 3, 9, -7, -15, 9, 27, -12, -45, 22, 66, -36, -99, 51, 153, -73, -222, 108, 311, -159, -441, 221, 624, -297, -863, 414, 1170, -575, -1584, 765, 2144, -1014, -2862, 1361, 3774, -1809, -4964, 2361, 6516, -3063, -8481

Offset: 0

N. J. A. Sloane

sign

Seiichi Manyama, Table of n, a(n) for n = 0..10000

Cf. A029838, A029839, A029841, A029842, A029843, A029844.

G.f.: x^(3/8)*theta_2(sqrt(x))^3/theta_2(x)^3, where theta_() is the Jacobi theta function. - Ilya Gutkovskiy, Dec 04 2017

A029842 Expansion of Product_{m>=1} ((1+q^(2m-1))/(1+q^(2m)))^5.

Original entry on oeis.org

1, 5, 5, -10, -10, 31, 20, -75, -40, 150, 84, -280, -165, 520, 290, -935, -495, 1595, 855, -2640, -1424, 4315, 2265, -6925, -3570, 10860, 5605, -16740, -8615, 25520, 12984, -38455, -19390, 57150, 28740, -83961, -42110, 122320

Offset: 0

N. J. A. Sloane

sign

Seiichi Manyama, Table of n, a(n) for n = 0..10000

Cf. A029838, A029839, A029840, A029841, A029843, A029844.

G.f.: x^(5/8)*theta_2(sqrt(x))^5/theta_2(x)^5, where theta_() is the Jacobi theta function. - Ilya Gutkovskiy, Dec 04 2017

A029843 Expansion of Product_{m>=1} ((1+q^(2m-1))/(1+q^(2m)))^6.

Original entry on oeis.org

1, 6, 9, -10, -24, 36, 65, -102, -153, 232, 327, -468, -663, 918, 1287, -1768, -2391, 3240, 4289, -5676, -7488, 9758, 12753, -16524, -21250, 27300, 34758, -44128, -55896, 70380, 88519, -110874, -138285, 172136, 213315

Offset: 0

N. J. A. Sloane

sign

Seiichi Manyama, Table of n, a(n) for n = 0..10000

Cf. A029838, A029839, A029840, A029841, A029842, A029844.

G.f.: x^(3/4)*theta_2(sqrt(x))^6/theta_2(x)^6, where theta_() is the Jacobi theta function. - Ilya Gutkovskiy, Dec 04 2017

A029844 Expansion of Product_{m>=1} ((1+q^(2m-1))/(1+q^(2m)))^7.

Original entry on oeis.org

1, 7, 14, -7, -42, 28, 133, -90, -357, 231, 833, -511, -1792, 1064, 3695, -2163, -7329, 4221, 13923, -7847, -25536, 14161, 45703, -25109, -80010, 43526, 136941, -73654, -229823, 122493, 379582, -200935, -617729, 324751

Offset: 0

N. J. A. Sloane

sign

Seiichi Manyama, Table of n, a(n) for n = 0..10000

Cf. A029838, A029839, A029840, A029841, A029842, A029843.

G.f.: x^(7/8)*theta_2(sqrt(x))^7/theta_2(x)^7, where theta_() is the Jacobi theta function. - Ilya Gutkovskiy, Dec 04 2017

A296043 a(n) = [x^n] Product_{k>=1} ((1 + x^(2k-1))/(1 + x^(2k)))^n.

Original entry on oeis.org

1, 1, -1, -5, -1, 31, 65, -90, -641, -644, 3329, 11386, -1471, -87021, -164634, 317935, 1881471, 1418719, -11370760, -33937951, 17468929, 294971868, 468897758, -1304743033, -6275603903, -2804572819, 42665919997, 109181454826, -106020803386, -1063546684834, -1362993953395

Offset: 0

Ilya Gutkovskiy, Dec 03 2017

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G. C. Greubel, Table of n, a(n) for n = 0..500

Main diagonal of A296067.

Cf. A029838, A029839, A029840, A029841, A029842, A029843, A029844, A029845, A296044, A296045.

Table[SeriesCoefficient[Product[((1 + x^(2 k - 1))/(1 + x^(2 k)))^n, {k, 1, n}], {x, 0, n}], {n, 0, 30}]
Table[SeriesCoefficient[(x^(1/8) EllipticTheta[2, 0, x^(1/2)]/EllipticTheta[2, 0, x])^n, {x, 0, n}], {n, 0, 30}]

A082304 McKay-Thompson series of class 16d for the Monster group.

Original entry on oeis.org

1, -2, -1, 2, 3, -2, -4, 4, 5, -8, -8, 10, 11, -12, -15, 18, 22, -26, -29, 34, 38, -42, -51, 56, 66, -78, -85, 98, 109, -120, -139, 156, 176, -202, -222, 250, 279, -306, -346, 384, 429, -482, -530, 590, 650, -714, -797, 876, 972, -1080, -1180, 1304, 1431, -1562, -1728, 1892, 2078, -2290, -2496

Offset: 0

Michael Somos, Apr 08 2003

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Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).

			T16d = 1/q - 2*q^3 - q^7 + 2*q^11 + 3*q^15 - 2*q^19 - 4*q^23 + 4*q^27 + ...

Seiichi Manyama, Table of n, a(n) for n = 0..1000
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
J. McKay and A. Sebbar, Fuchsian groups, automorphic functions and Schwarzians, Math. Ann., 318 (2000), 255-275. see page 273.
Michael Somos, Introduction to Ramanujan theta functions
Eric Weisstein's World of Mathematics, Ramanujan Theta Functions
Index entries for McKay-Thompson series for Monster simple group

Cf. A001936, A029839.

a[ n_] := SeriesCoefficient[ (QPochhammer[ x] / QPochhammer[ x^4])^2, {x, 0, n}]; (* Michael Somos, Jul 04 2014 *)

{a(n) = local(A); if( n<0, 0, A = x * O(x^n); polcoeff( (eta(x + A) / eta(x^4 + A))^2, n))};

Expansion of phi(-q) / psi(q^2) in powers of q where phi(), psi() are Ramanujan theta functions.
Expansion of q^(1/4) * (eta(q) / eta(q^4))^2 in powers of q.
Euler transform of period 4 sequence [ -2, -2, -2, 0, ...].
G.f. is a period 1 Fourier series which satisfies f(-1 / (64 t)) = 4 g(t) where q = exp(2 Pi i t) and g() is the g.f. for A001936. - Michael Somos, Jul 04 2014
Given g.f. A(x), then B(q) = A(q)^4 / q satisfies 0 = f(B(q), B(q^2)) where f(u, v) = v^2 - u * (16 + u) * (16 + v). - Michael Somos, Jul 04 2014
Given g.f. A(x), then B(q) = A(q^4) / q satisfies 0 = f(B(q), B(q^3)) where f(u, v) = (u^2 + v^2)^2 - u*v * (4 + u*v)^2. - Michael Somos, Aug 13 2007
Given g.f. A(x), then B(q) = A(q^4) / q satisfies 0 = f(B(q), B(q^5)) where f(u, v) = u*v * (16 + u^2*v^2)^2 - (u+v)^2 * (u^2 - 6*u*v + v^2)^2. - Michael Somos, Jul 04 2014
G.f.: Product_{k>0} ((1 - x^k) / (1 - x^(4*k)))^2.
a(n) = (-1)^n * A029839(n). Convolution inverse of A001936. - Michael Somos, Jul 04 2014
abs(a(n)) ~ exp(Pi*sqrt(n)/2) / (2^(3/2) * n^(3/4)). - Vaclav Kotesovec, Feb 07 2023

A162584 G.f.: A(x) = exp( 2Sum_{n>=1} sigma(n)A006519(n) * x^n/n ), where A006519(n) = highest power of 2 dividing n.

Original entry on oeis.org

1, 2, 8, 16, 50, 96, 240, 448, 1024, 1858, 3888, 6896, 13696, 23776, 44960, 76608, 139970, 234432, 414904, 684336, 1181568, 1921472, 3242928, 5206208, 8623104, 13679490, 22268752, 34941120, 56039936, 87036576, 137686048, 211822976

Offset: 0

Paul D. Hanna, Jul 06 2009

nonn

Log of the g.f. A(x) is formed from the term-wise product of the log of the g.f.s of the partition numbers A000041 and the binary partitions A000123.

			G.f.: A(x) = 1 + 2*x + 8*x^2 + 16*x^3 + 50*x^4 + 96*x^5 + 240*x^6 + ...
log(A(x))/2 = x + 6*x^2/2 + 4*x^3/3 + 28*x^4/4 + 6*x^5/5 + 24*x^6/6 + 8*x^7/7 + 120*x^8/8 + ... + sigma(n)*A006519(n)*x^n/n + ...
The log of the g.f. of the Partition numbers (A000041) is:
x + 3*x^2/2 + 4*x^3/3 + 7*x^4/4 + 6*x^5/5 + 12*x^6/6 + ... + sigma(n)*x^n/n + ...
The log of the g.f. of the binary partitions (A000123) is:
x + x^2/2 + x^3/3 + 4*x^4/4 + x^5/5 + 2*x^6/6 + x^7/7 + ... + A006519(n)*x^n/n + ...
From _Paul D. Hanna_, Jul 26 2009: (Start)
BISECTIONS begin:
B_0(q) = 1 + 8*q^2 + 50*q^4 + 240*q^6 + 1024*q^8 + 3888*q^10 + ...
B_1(q) = 2*q + 16*q^3 + 96*q^5 + 448*q^7 + 1858*q^9 + 6896*q^11 + ...
where 2*B_0(q)/B_1(q) = T16B(q):
T16B = 1/q + 2*q^3 - q^7 - 2*q^11 + 3*q^15 + 2*q^19 - 4*q^23 - 4*q^27 + ...
which is a g.f. of A029839. (End)

Vaclav Kotesovec, Table of n, a(n) for n = 0..10000 (terms 0..1000 from G. C. Greubel)

Cf. A000203, A006519, A000041, A000123.

Cf. A163228 (B_0), A163229 (B_1), A029839 (T16B); variant: A163129. - Paul D. Hanna, Jul 26 2009

eta[q_]:= q^(1/24)*QPochhammer[q]; nmax = 250; a[n_]:=SeriesCoefficient[ Series[Exp[Sum[DivisorSigma[1, k]*2^(IntegerExponent[k, 2] + 1)*q^k/k, {k, 1, nmax}]], {q, 0, nmax}], n]; Table[a[n], {n, 0, 50}] (* G. C. Greubel, Jul 03 2018 *)
nmax = 40; CoefficientList[Series[Exp[Sum[DivisorSigma[1, k]*2^(IntegerExponent[k, 2] + 1)*x^k/k, {k, 1, nmax}]], {x, 0, nmax}], x] (* Vaclav Kotesovec, Oct 20 2020 *)
nmax = 40; CoefficientList[Series[Product[1/EllipticTheta[4, 0, x^(2^k)]^(2^k), {k, 0, 1 + Log[2, nmax]}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Feb 07 2023 *)

{a(n)=local(L=sum(m=1,n,2*sigma(m)*2^valuation(m,2)*x^m/m)+x*O(x^n));polcoeff(exp(L),n)}

From Paul D. Hanna, Jul 26 2009: (Start)
Define series BISECTIONS A(q) = B_0(q) + B_1(q), then
2*B_0(q)/B_1(q) = T16B(q) = q*eta(q^8)^6/(eta(q^4)^2*eta(q^16)^4), the McKay-Thompson series of class 16B for the Monster group (A029839). (End)
G.f.: 1/Product_{n>=0} Theta4(q^(2^n))^(2^n) = 1 / ( E(1)^2*E(2)^3*E(4)^6*E(8)^12* ... * E(2^n)^A042950(n) * ... ) where E(n) = Product_{k>=1} (1-q^(n*k)). - Joerg Arndt, Mar 20 2010
Compare to the previous formula: 1/Product_{n>=0} Theta3(q^(2^n))^(2^n) = Theta4(q). - Joerg Arndt, Aug 03 2011

cp's OEIS Frontend

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A029842 Expansion of Product_{m>=1} ((1+q^(2*m-1))/(1+q^(2*m)))^5.

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A029843 Expansion of Product_{m>=1} ((1+q^(2*m-1))/(1+q^(2*m)))^6.

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A029844 Expansion of Product_{m>=1} ((1+q^(2*m-1))/(1+q^(2*m)))^7.

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A029840 Expansion of Product_{m>=1} ((1+q^(2m-1))/(1+q^(2m)))^3.

A029842 Expansion of Product_{m>=1} ((1+q^(2m-1))/(1+q^(2m)))^5.

A029843 Expansion of Product_{m>=1} ((1+q^(2m-1))/(1+q^(2m)))^6.

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A296043 a(n) = [x^n] Product_{k>=1} ((1 + x^(2k-1))/(1 + x^(2k)))^n.

A162584 G.f.: A(x) = exp( 2Sum_{n>=1} sigma(n)A006519(n) * x^n/n ), where A006519(n) = highest power of 2 dividing n.