cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-10 of 11 results. Next

A320139 Number of integer solutions to a^2 + 2*b^2 + 3*c^2 + 4*d^2 = n.

Original entry on oeis.org

1, 2, 2, 6, 8, 8, 16, 16, 14, 22, 24, 16, 22, 32, 12, 32, 44, 16, 42, 52, 36, 40, 64, 32, 40, 86, 24, 50, 72, 40, 60, 80, 38, 48, 112, 48, 72, 96, 64, 80, 120, 64, 48, 124, 52, 104, 96, 64, 106, 110, 110, 96, 144, 72, 128, 160, 60, 132, 120, 64, 144, 160, 60, 112, 164
Offset: 0

Views

Author

Seiichi Manyama, Oct 06 2018

Keywords

Comments

a(n) > 0 for n >= 0.

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[Product[EllipticTheta[3, 0, q^k], {k, 1, 4}], {q, 0, 70}], q] (* G. C. Greubel, Oct 29 2018 *)
  • PARI
    q='q+O('q^70); Vec(prod(k=1,4, eta(q^(2*k))^5/(eta(q^k)* eta(q^(4*k)))^2 )) \\ G. C. Greubel, Oct 29 2018

Formula

G.f.: theta_3(q) * theta_3(q^2) * theta_3(q^3) * theta_3(q^4).

A320138 Number of integer solutions to a^2 + 2*b^2 + 3*c^2 + 3*d^2 = n.

Original entry on oeis.org

1, 2, 2, 8, 10, 8, 24, 16, 10, 38, 8, 12, 48, 8, 32, 64, 26, 36, 70, 28, 24, 80, 28, 48, 96, 42, 40, 76, 48, 24, 112, 64, 58, 160, 68, 32, 126, 56, 44, 192, 56, 84, 176, 44, 60, 88, 80, 96, 208, 114, 74, 176, 72, 72, 172, 80, 112, 288, 88, 76, 224, 72, 112, 304, 90, 96
Offset: 0

Views

Author

Seiichi Manyama, Oct 06 2018

Keywords

Comments

a(n) > 0 for n >= 0.

Crossrefs

Formula

G.f.: theta_3(q) * theta_3(q^2) * theta_3(q^3)^2.

A320140 Number of integer solutions to a^2 + 2*b^2 + 3*c^2 + 5*d^2 = n.

Original entry on oeis.org

1, 2, 2, 6, 6, 6, 16, 8, 14, 26, 8, 32, 26, 8, 40, 16, 22, 40, 22, 32, 46, 40, 24, 48, 40, 42, 72, 50, 32, 64, 56, 28, 74, 48, 60, 112, 78, 24, 72, 76, 40, 144, 48, 48, 120, 50, 52, 48, 70, 98, 150, 128, 40, 84, 128, 52, 176, 120, 56, 208, 96, 72, 92, 72, 102, 192, 156
Offset: 0

Views

Author

Seiichi Manyama, Oct 06 2018

Keywords

Comments

a(n) > 0 for n >= 0.

Crossrefs

Formula

G.f.: theta_3(q) * theta_3(q^2) * theta_3(q^3) * theta_3(q^5).

A320188 Number of integer solutions to a^2 + 2*b^2 + 3*c^2 + 7*d^2 = n.

Original entry on oeis.org

1, 2, 2, 6, 6, 4, 12, 6, 6, 18, 12, 20, 26, 28, 20, 20, 34, 4, 30, 44, 20, 48, 44, 20, 20, 38, 16, 42, 62, 40, 56, 48, 34, 24, 72, 40, 70, 112, 36, 56, 68, 44, 40, 124, 60, 60, 124, 24, 66, 62, 54, 96, 92, 80, 64, 80, 64, 88, 136, 64, 76, 140, 52, 70, 166, 44, 104, 196, 44
Offset: 0

Views

Author

Seiichi Manyama, Oct 07 2018

Keywords

Comments

a(n) > 0 for n >= 0.

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[Product[EllipticTheta[3, 0, q^k], {k, 1, 3}]*EllipticTheta[3,0,q^7], {q, 0, 80}], q] (* G. C. Greubel, Oct 29 2018 *)
  • PARI
    q='q+O('q^80); Vec(prod(k=1,3, eta(q^(2*k))^5/(eta(q^k)* eta(q^(4*k)))^2 )*eta(q^(14))^5/(eta(q^7)* eta(q^(28)))^2 ) \\ G. C. Greubel, Oct 29 2018

Formula

G.f.: theta_3(q) * theta_3(q^2) * theta_3(q^3) * theta_3(q^7).

A320189 Number of integer solutions to a^2 + 2*b^2 + 3*c^2 + 8*d^2 = n.

Original entry on oeis.org

1, 2, 2, 6, 6, 4, 12, 4, 4, 18, 4, 20, 30, 12, 36, 24, 10, 32, 14, 24, 48, 32, 36, 40, 24, 18, 28, 34, 36, 60, 60, 28, 28, 40, 16, 56, 78, 44, 108, 68, 8, 72, 24, 40, 144, 60, 72, 112, 30, 46, 42, 64, 84, 116, 120, 40, 72, 84, 28, 116, 96, 60, 180, 68, 34, 120, 60, 64, 192, 80
Offset: 0

Views

Author

Seiichi Manyama, Oct 07 2018

Keywords

Comments

a(n) > 0 for n >= 0.

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[Product[EllipticTheta[3, 0, q^k], {k, 1, 3}]*EllipticTheta[3,0,q^8], {q, 0, 80}], q] (* G. C. Greubel, Oct 29 2018 *)
  • PARI
    q='q+O('q^80); Vec(prod(k=1,3, eta(q^(2*k))^5/(eta(q^k)* eta(q^(4*k)))^2 )*eta(q^(16))^5/(eta(q^8)* eta(q^(32)))^2 ) \\ G. C. Greubel, Oct 29 2018

Formula

G.f.: theta_3(q) * theta_3(q^2) * theta_3(q^3) * theta_3(q^8).

A320190 Number of integer solutions to a^2 + 2*b^2 + 3*c^2 + 9*d^2 = n.

Original entry on oeis.org

1, 2, 2, 6, 6, 4, 12, 4, 2, 16, 4, 12, 30, 16, 20, 40, 14, 8, 42, 8, 28, 60, 20, 32, 44, 22, 8, 46, 28, 36, 84, 36, 18, 40, 32, 8, 80, 40, 40, 120, 36, 24, 56, 40, 44, 140, 48, 48, 126, 22, 62, 64, 40, 68, 132, 72, 52, 120, 52, 60, 136, 56, 36, 160, 46, 64, 180, 40, 48
Offset: 0

Views

Author

Seiichi Manyama, Oct 07 2018

Keywords

Comments

a(n) > 0 for n >= 0.

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[Product[EllipticTheta[3, 0, q^k], {k, 1, 3}]*EllipticTheta[3,0,q^9], {q, 0, 80}], q] (* G. C. Greubel, Oct 29 2018 *)
  • PARI
    q='q+O('q^80); Vec(prod(k=1,3, eta(q^(2*k))^5/(eta(q^k)* eta(q^(4*k)))^2 )*eta(q^(18))^5/(eta(q^9)* eta(q^(36)))^2 ) \\ G. C. Greubel, Oct 29 2018

Formula

G.f.: theta_3(q) * theta_3(q^2) * theta_3(q^3) * theta_3(q^9).

A320191 Number of integer solutions to a^2 + 2*b^2 + 3*c^2 + 10*d^2 = n.

Original entry on oeis.org

1, 2, 2, 6, 6, 4, 12, 4, 2, 14, 2, 12, 22, 16, 24, 24, 30, 12, 18, 36, 12, 40, 48, 16, 36, 42, 12, 26, 40, 28, 60, 60, 26, 32, 36, 28, 42, 48, 36, 60, 74, 40, 8, 52, 60, 52, 132, 40, 46, 114, 14, 72, 48, 36, 120, 96, 72, 60, 64, 60, 100, 124, 60, 68, 126, 52, 60, 124
Offset: 0

Views

Author

Seiichi Manyama, Oct 07 2018

Keywords

Comments

a(n) > 0 for n >= 0.

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[Product[EllipticTheta[3, 0, q^k], {k, 1, 3}]*EllipticTheta[3,0,q^10], {q, 0, 80}], q] (* G. C. Greubel, Oct 29 2018 *)
  • PARI
    q='q+O('q^80); Vec(prod(k=1,3, eta(q^(2*k))^5/(eta(q^k)* eta(q^(4*k)))^2 )*eta(q^(20))^5/(eta(q^10)* eta(q^(40)))^2 ) \\ G. C. Greubel, Oct 29 2018

Formula

G.f.: theta_3(q) * theta_3(q^2) * theta_3(q^3) * theta_3(q^10).

A319822 Number of solutions to x^2 + 2*y^2 + 5*z^2 + 5*w^2 = n.

Original entry on oeis.org

1, 2, 2, 4, 2, 4, 12, 8, 18, 14, 4, 28, 12, 24, 32, 0, 34, 20, 14, 28, 4, 32, 44, 40, 28, 10, 40, 56, 64, 72, 8, 48, 66, 24, 68, 8, 46, 88, 60, 32, 4, 52, 64, 116, 76, 12, 64, 72, 60, 82, 26, 72, 104, 104, 88, 8, 112, 56, 136, 140, 8, 136, 96, 72, 98, 16, 72, 132
Offset: 0

Views

Author

Jianing Song, Sep 28 2018

Keywords

Comments

Ramanujan (1917) claimed that there are exactly 55 possible choice for a <= b <= c <= d such that a*x^2 + b*y^2 + c*z^2 + d*w^2 represents all natural numbers, but L. E. Dickson (1927) has pointed out that Ramanujan has overlooked the fact that (1, 2, 5, 5) does not represent 15. Consequently, there are only 54 forms. This sequence is related to the form (1, 2, 5, 5). As is proven, a(n) = 0 iff n = 15.
There are also many (a, b, c, d) other than this such that a*x^2 + b*y^2 + c*z^2 + d*w^2 represents all but finitely many natural numbers. For example, x^2 + y^2 + 5*z^2 + 5*w^2 represents all natural numbers except for 3 (cf. A236929); x^2 + y^2 + z^2 + d*w^2 (d == 2 (mod 4) or d = 9, 17, 25, 36, 68, 100 and some others) represents all natural numbers except for those of the form 4^i*(8*j + 7) and < d; x^2 + 2*y^2 + 6*z^2 + d*w^2 (d == 2 (mod 4) or d = 11, 19 and some others) represents all natural numbers except for those of the form 4^i*(8*j + 5) and < d.

Examples

			a(5) = 4 because 0^2 + 2*0^2 + 5*0^2 + 5*1^2 = 0^2 + 2*0^2 + 5*0^2 + 5*(-1)^2 = 0^2 + 2*0^2 + 5*1^2 + 5*0^2 = 0^2 + 2*0^2 + 5*(-1)^2 + 5*0^2 = 5 and these are the only four solutions to x^2 + 2*y^2 + 5*z^2 + 5*w^2 = 5.
		

References

  • J. H. Conway, Universal quadratic forms and the fifteen theorem, Contemporary Mathematics 272 (1999), 23-26.

Crossrefs

From Seiichi Manyama, Oct 07 2018: (Start)
54 possible choice:
k | a, b, c, d | Number of solutions
------+-----------------+--------------------
1 | 1, 1, 1, 1 | A000118
2 | 1, 1, 1, 2 | A236928
3 | 1, 1, 1, 3 | A236926
4 | 1, 1, 1, 4 | A236923
5 | 1, 1, 1, 5 | A236930
6 | 1, 1, 1, 6 | A236931
7 | 1, 1, 1, 7 | A236932
8 | 1, 1, 2, 2 | A097057
9 | 1, 1, 2, 3 | A320124
10 | 1, 1, 2, 4 | A320125
11 | 1, 1, 2, 5 | A320126
12 | 1, 1, 2, 6 | A320127
13 | 1, 1, 2, 7 | A320128
14 | 1, 1, 2, 8 | A320130
15 | 1, 1, 2, 9 | A320131
16 | 1, 1, 2, 10 | A320132
17 | 1, 1, 2, 11 | A320133
18 | 1, 1, 2, 12 | A320134
19 | 1, 1, 2, 13 | A320135
20 | 1, 1, 2, 14 | A320136
21 | 1, 1, 3, 3 | A034896
22 | 1, 1, 3, 4 | A272364
23 | 1, 1, 3, 5 | A320147
24 | 1, 1, 3, 6 | A320148
25 | 1, 2, 2, 2 | A320149
26 | 1, 2, 2, 3 | A320150
27 | 1, 2, 2, 4 | A236924
28 | 1, 2, 2, 5 | A320151
29 | 1, 2, 2, 6 | A320152
30 | 1, 2, 2, 7 | A320153
31 | 1, 2, 3, 3 | A320138
32 | 1, 2, 3, 4 | A320139
33 | 1, 2, 3, 5 | A320140
34 | 1, 2, 3, 6 | A033712
35 | 1, 2, 3, 7 | A320188
36 | 1, 2, 3, 8 | A320189
37 | 1, 2, 3, 9 | A320190
38 | 1, 2, 3, 10 | A320191
39 | 1, 2, 4, 4 | A320193
40 | 1, 2, 4, 5 | A320194
41 | 1, 2, 4, 6 | A320195
42 | 1, 2, 4, 7 | A320196
43 | 1, 2, 4, 8 | A033720
44 | 1, 2, 4, 9 | A320197
45 | 1, 2, 4, 10 | A320198
46 | 1, 2, 4, 11 | A320199
47 | 1, 2, 4, 12 | A320200
48 | 1, 2, 4, 13 | A320201
49 | 1, 2, 4, 14 | A320202
50 | 1, 2, 5, 6 | A320163
51 | 1, 2, 5, 7 | A320164
52 | 1, 2, 5, 8 | A320165
53 | 1, 2, 5, 9 | A320166
54 | 1, 2, 5, 10 | A033722
(End)

Programs

  • Maple
    JT := (k, n) -> JacobiTheta3(0, x^k)^n:
    A319822List := proc(len) series(JT(1,1)*JT(2,1)*JT(5,2), x, len+1);
    seq(coeff(%, x, j), j=0..len) end: A319822List(67); # Peter Luschny, Oct 01 2018
  • Mathematica
    CoefficientList[EllipticTheta[3, 0, q] EllipticTheta[3, 0, q^2] EllipticTheta[ 3, 0, q^5]^2 + O[q]^100, q] (* Jean-François Alcover, Jun 15 2019 *)
  • PARI
    A004018(n) = if(n, 4*sumdiv(n,d,kronecker(-4,d)), 1);
    A033715(n) = if(n, 2*sumdiv(n,d,kronecker(-2,d)), 1);
    a(n) = my(i=0); for(k=0, n\5, i+=A004018(k)*A033715(n-5*k)); i
    
  • PARI
    N=99; q='q+O('q^N);
    gf = (eta(q^2)*eta(q^4))^3*eta(q^10)^10/(eta(q)*eta(q^5)^2*eta(q^8)*eta(q^20)^2)^2;
    Vec(gf) \\ Altug Alkan, Oct 01 2018
    
  • Sage
    Q = DiagonalQuadraticForm(ZZ, [1, 2, 5, 5])
    Q.theta_series(68).list() # Peter Luschny, Oct 01 2018

Formula

a(n) = Sum_{k=0..floor(n/5)} A004018(k)*A033715(n-5*k).
G.f.: theta_3(q)*theta_3(q^2)*theta_3(q^5)^2, where theta_3() is the Jacobi theta function.

A282544 Expansion of (phi(x)^4 + 3*phi(x^3)^4) / 4 in powers of x where phi() is a Ramanujan theta function.

Original entry on oeis.org

1, 2, 6, 14, 6, 12, 42, 16, 6, 50, 36, 24, 42, 28, 48, 84, 6, 36, 150, 40, 36, 112, 72, 48, 42, 62, 84, 158, 48, 60, 252, 64, 6, 168, 108, 96, 150, 76, 120, 196, 36, 84, 336, 88, 72, 300, 144, 96, 42, 114, 186, 252, 84, 108, 474, 144, 48, 280, 180, 120, 252
Offset: 0

Views

Author

Michael Somos, Feb 17 2017

Keywords

Comments

Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).
Cubic AGM theta functions: a(q) (see A004016), b(q) (A005928), c(q) (A005882).
a(n) is the number of solutions in integers to n = x^2 + y^2 + z^2 + w^2 where x + y + z = 3m is a multiple of 3. - Michael Somos, Jun 23 2018

Examples

			G.f. = 1 + 2*x + 6*x^2 + 14*x^3 + 6*x^4 + 12*x^5 + 42*x^6 + 16*x^7 + 6*x^8 + ...
a(4) = 6 with solutions (x, y, z, w) = {(1, 1, 1, 1), (1, 1, 1, -1), (0, 0, 0, 2)} and their negatives. - _Michael Somos_, Jun 23 2018
		

Crossrefs

Programs

  • Magma
    A := Basis( ModularForms( Gamma0(12), 2), 60); A[1] + 2*A[2] + 6*A[3] + 14*A[4] + 6*A[5];
  • Mathematica
    a[ n_] := If[ n < 1, Boole[n == 0], 2 DivisorSum[n, # {1, 1, 2, 0, 1, 2, 1, 0, 2, 1, 1, 0}[[Mod[#, 12, 1]]] &]];
    a[ n_] := If[ n < 1, Boole[n == 0], 2 Times @@ (Which[# < 3, 2 + (-1)^#, # == 3, 3^(#2 + 1) - 2, True, (#^(#2 + 1) - 1) / (# - 1)] & @@@ FactorInteger@n)];
    a[ n_] := SeriesCoefficient[ (EllipticTheta[ 3, 0, x]^4 + 3 * EllipticTheta[ 3, 0, x^3]^4) / 4, {x, 0, n}];
  • PARI
    {a(n) = if( n<1, n==0, 2 * sumdiv(n, d, d * [0, 1, 1, 2, 0, 1, 2, 1, 0, 2, 1, 1][d%12+1]))};
    
  • PARI
    {a(n) = if( n<1, n==0, my(A = factor(n), p, e); 2 * prod(k=1, matsize(A)[1], [p, e] = A[k, ]; if( p==2, 3, p==3, 3^(e+1) - 2, (p^(e+1) - 1) / (p - 1))))};
    
  • PARI
    {a(n) = if( n<0, 0, my(A); A = x * O(x^n); polcoeff( (sum(k=1, sqrtint(n), 2 * x^k^2, 1 + A)^4 + 3 * sum(k=1, sqrtint(n\3), 2 * x^(3*k^2), 1 + A)^4) / 4, n))};
    

Formula

Expansion of a(x^2) * phi(x) * phi(x^3) in powers of x where a() is a cubic AGM theta function and phi() is a Ramanujan theta function.
Expansion of (chi(x) * chi(x^3))^3 * (psi(x)^4 + 3*x*psi(x^3)^4) in powers of x where psi(), chi() are Ramanujan theta functions.
a(n) = 2*b(n) where b() is multiplicative with a(0) = 1, b(2^e) = 3 if e>0, b(3^e) = 3^(e+1) - 2, b(p^e) = (p^(e+1) - 1) / (p - 1) if p>3.
G.f. is a period 1 Fourier series which satisfies f(-1 / (12 t)) = 12 (t/i)^2 f(t) where q = exp(2 Pi i t).
G.f.: ((Sum_{k in Z} x^k^2)^4 + 3 * (Sum_{k in Z} x^(3*k^2))^4) / 4.
G.f.: 1 + 2 * Sum_{k>0} F(k, x) + 6 * Sum_{k>0} F(3*k, x) where F(k, x) = x^k / (1 + (-x)^k)^2.
G.f.: 1 + 2 * Sum_{k>0} F(k, x) + 2 * Sum_{k>0} F(3*k, x) where F(k, x) = k * x^k / (1 + (-x)^k).
a(2*n) = A125510(n). a(n) = A033712(2*n).
Sum_{k=1..n} a(k) ~ c * n^2, where c = Pi^2/6 = 1.644934... (A013661). - Amiram Eldar, Dec 29 2023

A028977 Theta series of 8-d 6-modular lattice G_2 tensor F_4 (or A_2 tensor D_4) with det 1296 and minimal norm 4 in powers of q^2.

Original entry on oeis.org

1, 0, 72, 192, 504, 576, 2280, 1728, 4248, 4800, 7920, 6336, 19416, 10368, 21312, 22464, 33624, 24192, 63048, 32832, 65808, 60864, 83232, 57600, 155640, 76032, 137520, 130944, 180288, 116928, 290736
Offset: 0

Views

Author

Keywords

Comments

Proposition 7.6 [McKay and Sebbar, 2000, p. 272, equ. (7.8)] expresses the theta series as a Schwarzian of A007258 and tau. - Michael Somos, Jun 05 2015

Examples

			G.f. = 1 + 72*x^2 + 192*x^3 + 504*x^4 + 576*x^5 + 2280*x^6 + 1728*x^7 + ...
G.f. = 1 + 72*q^4 + 192*q^6 + 504*q^8 + 576*q^10 + 2280*q^12 + 1728*q^14 + ...
		

Crossrefs

Programs

  • Magma
    A := Basis( ModularForms( Gamma0(6), 4), 32); A[1] + 72*A[3] + 192*A[4] + 504*A[5]; /* Michael Somos, Aug 20 2014 */
  • Mathematica
    a[ n_] := SeriesCoefficient[ With[{e1 = QPochhammer[ x] QPochhammer[ x^6], e2 = QPochhammer[ x^2] QPochhammer[ x^3]}, (e2^7 / e1^5 - x e1^7 /e2^5)^2 - 8 x (e1 e2)^2], {x, 0, n}]; (* Michael Somos, Apr 19 2015 *)
  • PARI
    {a(n) = local(A, B); if( n<0, 0, A = x * O(x^n); B = eta(x^2 + A) * eta(x^3 + A); A = eta(x + A) * eta(x^6 + A); polcoeff( (B^7 / A^5 - x * A^7 / B^5)^2 - 8 * x * (A * B)^2, n))}; /* Michael Somos, May 27 2012 */
    

Formula

Expansion of ((eta(q^2) * eta(q^3))^7 / (eta(q) * eta(q^6))^5 - (eta(q) * eta(q^6))^7 / (eta(q^2) * eta(q^3))^5)^2 - 8 * (eta(q^2) * eta(q^4) * eta(q^6) * eta(q^12))^2 in powers of q. - Michael Somos, May 27 2012
A212817(n) = a(n) + 8 * A030209(n). - Michael Somos, May 27 2012
G.f. A(x) = g1(x)^2 * (1 - 4*g2(x) - 16*g2(x)^3 + 16*g2(x)^4) where g1(x) = A033712(x) and g2(x) = A212770(x). - Michael Somos, Apr 19 2015
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