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 1-8 of 8 results.

A097451 Number of partitions of n into parts congruent to {2, 3, 4} mod 6.

Original entry on oeis.org

1, 0, 1, 1, 2, 1, 3, 2, 5, 4, 7, 6, 11, 9, 15, 14, 22, 20, 31, 29, 43, 41, 58, 57, 80, 78, 106, 107, 142, 143, 188, 191, 247, 253, 321, 332, 418, 432, 537, 561, 690, 721, 880, 924, 1118, 1178, 1412, 1493, 1781, 1884, 2231, 2370, 2789, 2965, 3472, 3698, 4309, 4596
Offset: 0

Views

Author

Vladeta Jovovic, Aug 23 2004

Keywords

Comments

Number of partitions of n in which no part is 1, no part appears more than twice and no two parts differ by 1. Example: a(6)=3 because we have [6],[4,2] and [3,3]. - Emeric Deutsch, Feb 16 2006
Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).

Examples

			a(8)=5 because we have [8],[44],[422],[332] and [2222].
G.f. = 1 + x^2 + x^3 + 2*x^4 + x^5 + 3*x^6 + 2*x^7 + 5*x^8 + 4*x^9 + ...
G.f. = q^7 + q^55 + q^79 + 2*q^103 + q^127 + 3*q^151 + 2*q^175 + 5*q^199 + ...
		

References

  • G. E. Andrews, The Theory of Partitions, Addison-Wesley, 1976, Exercise 7.9.

Crossrefs

Programs

  • Haskell
    a097451 n = p a047228_list n where
       p _  0         = 1
       p ks'@(k:ks) m = if m < k then 0 else p ks' (m - k) + p ks m
    -- Reinhard Zumkeller, Nov 16 2012
    
  • Maple
    g:=1/product((1-x^(2+6*j))*(1-x^(3+6*j))*(1-x^(4+6*j)),j=0..15): gser:=series(g,x=0,75): seq(coeff(gser,x,n),n=0..67); # Emeric Deutsch, Feb 16 2006
  • Mathematica
    a[ n_] := SeriesCoefficient[ 1 / Product[ 1 - Boole[ OddQ[ Quotient[ k + 1, 3]]] x^k, {k, n}], {x, 0, n}]; (* Michael Somos, Sep 24 2013 *)
    a[ n_] := SeriesCoefficient[ QPochhammer[ -x^3, x^3] QPochhammer[ x^6] / QPochhammer[ x^2], {x, 0, n}]; (* Michael Somos, Sep 24 2013 *)
  • PARI
    {a(n) = if( n<0, 0, polcoeff( 1 / prod(k=1, n, 1 - ( (k+1)\3 % 2) * x^k, 1 + x * O(x^n)), n))}; /* Michael Somos, Sep 24 2013 */
    
  • PARI
    {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^6 + A)^2 / (eta(x^2 + A) * eta(x^3 + A)), n))}; /* Michael Somos, Sep 24 2013 */

Formula

Euler transform of period 6 sequence [ 0, 1, 1, 1, 0, 0, ...].
G.f.: 1/Product_{j>=0} ((1-x^(2+6j))(1-x^(3+6j))(1-x^(4+6j))). - Emeric Deutsch, Feb 16 2006
Expansion of psi(x^3) / f(-x^2) in powers of x where psi(), f() are Ramanujan theta functions. - Michael Somos, Sep 24 2013
Expansion of q^(-7/24) * eta(q^6)^2 / (eta(q^2) * eta(q^3)) in powers of q. - Michael Somos, Sep 24 2013
a(n) ~ exp(Pi*sqrt(n/3)) / (4*3^(3/4)*n^(3/4)). - Vaclav Kotesovec, Aug 30 2015
Expansion of f(-x, -x^5) / f(-x, -x^2) in powers of x where f(, ) is Ramanujan's general theta function. - Michael Somos, Oct 06 2015

Extensions

More terms from Emeric Deutsch, Feb 16 2006

A108961 Number of partitions that are "2-close" to being self-conjugate.

Original entry on oeis.org

1, 1, 2, 3, 3, 5, 7, 9, 12, 16, 20, 26, 33, 41, 51, 64, 79, 97, 119, 144, 175, 212, 254, 305, 365, 434, 516, 612, 722, 851, 1002, 1174, 1375, 1607, 1872, 2179, 2531, 2933, 3395, 3923, 4524, 5211, 5994, 6881, 7891, 9038, 10334, 11804, 13467, 15341, 17460, 19849
Offset: 0

Views

Author

John McKay (mckay(AT)cs.concordia.ca), Jul 22 2005

Keywords

Comments

Let (a1,a2,a3,...ad:b1,b2,b3,...bd) be the Frobenius symbol for a partition pi of n. Then pi is m-close to being self-conjugate if for all k, |ak-bk| <= m.
Convolution of A070048 and A035457. - Vaclav Kotesovec, Nov 13 2016

Examples

			1 + x + 2*x^2 + 3*x^3 + 3*x^4 + 5*x^5 + 7*x^6 + 9*x^7 + 12*x^8 + 16*x^9 + 20*x^10 + ...
1/q + q^23 + 2*q^47 + 3*q^71 + 3*q^95 + 5*q^119 + 7*q^143 + 9*q^167 + 12*q^191 + ...
		

References

  • D. M. Bressoud, Analytic and combinatorial generalizations of the Rogers-Ramanujan identities, Mem. Amer. Math. Soc. 24 (1980), no. 227, 54 pp.

Crossrefs

Cf. A000700 for m=0 (self-conjugate), A070047 for m=1, A108962 for m=3, A271661 for m=4, A280937 for m=5, A280938 for m=6.

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[Product[(1 + x^k) * (1 + x^(2*k)) / (1 + x^(4*k)), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Nov 13 2016 *)
  • PARI
    {a(n) = local(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^4 + A)^2 / (eta(x + A) * eta(x^8 + A)), n))} /* Michael Somos, Oct 17 2006 */

Formula

Define the Dedekind eta function = q^1/24. Product(1-q^k), k >=1. Then the number of m-close partitions is q^(1/24).(m+2)^2/(1.(2m+4)) (where m denotes eta(q^m)).
Expansion of q^(1/24) * eta(q^4)^2 / (eta(q) * eta(q^8)) in powers of q. - Michael Somos, Oct 17 2006
Expansion of chi(x^2) * chi(x) / chi(-x^2) in powers of x where chi() is a Ramanujan theta function (see A000700). - Michael Somos, Oct 17 2006 [corrected by Peter Bala, Oct 09 2023]
Euler transform of period 8 sequence [ 1, 1, 1, -1, 1, 1, 1, 0, ...]. - Michael Somos, Oct 17 2006
G.f.: Product_{k>0} (1 + x^k) * (1 + x^(2*k)) / (1 + x^(4*k)). - Michael Somos, Oct 17 2006
a(n) ~ Pi * BesselI(1, Pi * sqrt(5*(24*n-1)/2)/12) / (2*sqrt((24*n-1)/5)) ~ 5^(1/4) * exp(sqrt(5*n/3)*Pi/2) / (2^(5/2) * 3^(1/4) * n^(3/4)) * (1 -(3*sqrt(3) / (4*Pi*sqrt(5)) + Pi*sqrt(5)/(96*sqrt(3)))/sqrt(n) + (5*Pi^2/55296 - 9/(32*Pi^2) + 5/128)/n). - Vaclav Kotesovec, Nov 13 2016, extended Jan 11 2017

A108962 Number of partitions that are "3-close" to being self-conjugate.

Original entry on oeis.org

1, 1, 2, 3, 5, 5, 9, 11, 16, 20, 28, 34, 47, 57, 75, 92, 119, 143, 183, 220, 277, 332, 412, 491, 605, 718, 874, 1036, 1252, 1475, 1772, 2082, 2483, 2909, 3450, 4027, 4755, 5533, 6499, 7545, 8826, 10213, 11904, 13741, 15955, 18372, 21262, 24422
Offset: 0

Views

Author

John McKay (mckay(AT)cs.concordia.ca), Jul 22 2005

Keywords

Comments

Let (a1,a2,a3,...ad:b1,b2,b3,...bd) be the Frobenius symbol for a partition pi of n. Then pi is m-close to being self-conjugate if for all k, |ak-bk| <= m.

Examples

			1 + x + 2*x^2 + 3*x^3 + 5*x^4 + 5*x^5 + 9*x^6 + 11*x^7 + 16*x^8 + 20*x^9 + 28*x^10 + ...
1/q + q^23 + 2*q^47 + 3*q^71 + 5*q^95 + 5*q^119 + 9*q^143 + 11*q^167 + 16*q^191 + ...
		

References

  • D. M. Bressoud, Analytic and combinatorial generalizations of the Rogers-Ramanujan identities, Mem. Amer. Math. Soc. 24 (1980), no. 227, 54 pp.

Crossrefs

Cf. A000700 for m=0 (self-conjugate), A070047 for m=1, A108961 for m=2, A271661 for m=4, A280937 for m=5, A280938 for m=6.

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[Product[(1 - x^(5*k))^2 / ((1 - x^k) * (1 - x^(10*k))), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Nov 13 2016 *)
  • PARI
    {a(n) = local(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^5 + A)^2 / (eta(x + A) * eta(x^10 + A)), n))} /* Michael Somos, Jun 08 2012 */

Formula

Define the Dedekind eta function = q^1/24. Product(1-q^k), k >=1. Then the number of m-close partitions is q^(1/24).(m+2)^2/(1.(2m+4)) (where m denotes eta(q^m)).
From Vaclav Kotesovec, Nov 13 2016, extended Jan 11 2017: (Start)
a(n, m) ~ exp(Pi*sqrt((2*m+1)*n/(3*(m+2)))) * (2*m+1)^(1/4) / (2*3^(1/4)*(m+2)^(3/4)*n^(3/4)).
For m=3, a(n) ~ 7^(1/4) * exp(sqrt(7*n/15)*Pi) / (2*3^(1/4)*5^(3/4)*n^(3/4)) * (1 -(3*sqrt(15)/(8*Pi*sqrt(7)) + Pi*sqrt(7)/(48*sqrt(15)))/sqrt(n) + (7*Pi^2/69120 - 225/(896*Pi^2) + 5/128)/n).
(End)
a(n) ~ 2*Pi * BesselI(1, Pi/6 * sqrt((24*n-1)*7/10)) / (5*sqrt((24*n-1)/7)). - Vaclav Kotesovec, Jan 11 2017

A271661 Expansion of phi(-x^6) / f(-x) in powers of x where phi(), f() are Ramanujan theta functions.

Original entry on oeis.org

1, 1, 2, 3, 5, 7, 9, 13, 18, 24, 32, 42, 55, 71, 91, 116, 147, 185, 231, 288, 357, 440, 540, 661, 807, 980, 1186, 1432, 1724, 2069, 2476, 2956, 3521, 4183, 4958, 5865, 6923, 8155, 9587, 11251, 13180, 15411, 17990, 20967, 24399, 28348, 32886, 38098, 44075
Offset: 0

Views

Author

Michael Somos, Apr 11 2016

Keywords

Comments

Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).
Partitions which are "4-close" to being self-conjugate; see A108961 for the definition. - Arvind Ayyer, Apr 13 2021

Examples

			G.f. = 1 + x + 2*x^2 + 3*x^3 + 5*x^4 + 7*x^5 + 9*x^6 + 13*x^7 + 18*x^8 + ...
G.f. = q^-1 + q^23 + 2*q^47 + 3*q^71 + 5*q^95 + 7*q^119 + 9*q^143 + 13*q^167 + ..
		

References

  • D. M. Bressoud, Analytic and combinatorial generalizations of the Rogers-Ramanujan identities, Mem. Amer. Math. Soc. 24 (1980), no. 227, 54 pp.
  • Srinivasa Ramanujan, The Lost Notebook and Other Unpublished Papers, Narosa Publishing House, New Delhi, 1988. See page 6 equation 2.

Crossrefs

Programs

  • Mathematica
    a[ n_] := SeriesCoefficient[ EllipticTheta[ 4, 0, x^6] / QPochhammer[ x], {x, 0, n}];
    a[ n_] := If[ n < 0, 0, SeriesCoefficient[ Sum[ x^k^2 QPochhammer[ -x, x^2, k] / QPochhammer[ x, x, 2 k] // FunctionExpand, {k, 0, Sqrt@n}], {x, 0, n}]];
    nmax = 50; CoefficientList[Series[Product[(1-x^(6*k)) / ((1-x^k) * (1+x^(6*k))), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Apr 18 2016 *)
  • PARI
    {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^6 + A)^2 / (eta(x + A) * eta(x^12 + A)), n))};

Formula

Expansion of f(x^2, x^4) / psi(-x) in powers of x where psi(), f(, ) are Ramanujan theta functions.
Expansion of q^(1/24) * eta(q^6)^2 / (eta(q) * eta(q^12)) in powers of q.
Euler transform of period 12 sequence [ 1, 1, 1, 1, 1, -1, 1, 1, 1, 1, 1, 0, ...].
G.f.: Sum_{k>=0} x^(k^2) (-x, x^2)k / (x){2*k}.
a(n) ~ Pi * BesselI(1, Pi*sqrt(24*n-1)/(4*sqrt(3))) / sqrt(24*n-1) ~ exp(sqrt(n/2)*Pi) / (2^(7/4)*sqrt(3)*n^(3/4)) * (1 - (3/(4*Pi) + Pi/48)/sqrt(2*n) + (5/128 - 15/(64*Pi^2) + Pi^2/9216)/n). - Vaclav Kotesovec, Apr 18 2016, extended Jan 10 2017

A280937 Expansion of Product_{k>=1} ((1 - x^(7*(2*k-1))) * (1 - x^(7*k)) / (1 - x^k)).

Original entry on oeis.org

1, 1, 2, 3, 5, 7, 11, 13, 20, 26, 36, 46, 63, 79, 105, 132, 171, 213, 273, 336, 425, 522, 650, 793, 981, 1188, 1456, 1756, 2136, 2563, 3098, 3698, 4443, 5285, 6312, 7477, 8891, 10489, 12415, 14599, 17206, 20165, 23678, 27659, 32363, 37698, 43958, 51058, 59361
Offset: 0

Views

Author

Vaclav Kotesovec, Jan 11 2017

Keywords

References

  • D. M. Bressoud, Analytic and combinatorial generalizations of the Rogers-Ramanujan identities, Mem. Amer. Math. Soc. 24 (1980), no. 227, 54 pp.

Crossrefs

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[Product[(1-x^(7*(2*k-1))) * (1-x^(7*k)) / (1-x^k), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ 2*Pi * BesselI(1, Pi/6 * sqrt(11*(24*n-1)/14)) / (7*sqrt((24*n-1)/11)).
a(n) ~ exp(Pi * sqrt(11*n/21)) * 11^(1/4) / (2 * 3^(1/4) * 7^(3/4) * n^(3/4)) * (1 -(3*sqrt(21)/(8*Pi*sqrt(11)) + Pi*sqrt(11)/(48*sqrt(21)))/sqrt(n) + (11*Pi^2/96768 - 315/(1408*Pi^2) + 5/128)/n).

A280938 Expansion of Product_{k>=1} (1 - x^(8*(2*k-1))) * (1 - x^(8*k)) / (1 - x^k).

Original entry on oeis.org

1, 1, 2, 3, 5, 7, 11, 15, 20, 28, 38, 50, 67, 87, 113, 146, 187, 237, 301, 378, 473, 590, 732, 903, 1113, 1364, 1666, 2030, 2464, 2981, 3600, 4332, 5201, 6229, 7442, 8869, 10551, 12521, 14829, 17531, 20684, 24357, 28638, 33607, 39375, 46062, 53798, 62736
Offset: 0

Views

Author

Vaclav Kotesovec, Jan 11 2017

Keywords

Comments

In general, if r>=2 and g.f. = Product_{k>=1} (1-x^(r*(2*k-1))) * (1-x^(r*k)) / (1-x^k), then
a(n, r) ~ 2*Pi * BesselI(1, Pi/6 * sqrt((24*n-1)*(2*r-3)/(2*r))) / (r*sqrt((24*n-1)/(2*r-3))).
a(n, r) ~ exp(Pi * sqrt((2/3 - 1/r)*n)) * (2*r-3)^(1/4) / (2 * 3^(1/4) * r^(3/4) * n^(3/4)) * (1 -(3*sqrt(3*r)/(8*Pi*sqrt(2*r-3)) + Pi*sqrt(2*r-3)/(48*sqrt(3*r))) / sqrt(n) + (Pi^2*(2*r-3)/(13824*r) - 45*r/(128*Pi^2*(2*r-3)) + 5/128)/n).

References

  • D. M. Bressoud, Analytic and combinatorial generalizations of the Rogers-Ramanujan identities, Mem. Amer. Math. Soc. 24 (1980), no. 227, 54 pp.

Crossrefs

Cf. A000700 (r=2), A070047 (r=3), A108961 (r=4), A108962 (r=5), A271661 (r=6), A280937 (r=7).

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[Product[(1-x^(8*(2*k-1))) * (1-x^(8*k)) / (1-x^k), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ Pi * BesselI(1, Pi * sqrt(13*(24*n-1))/24) / (4*sqrt((24*n-1)/13)).
a(n) ~ exp(Pi*sqrt(13*n/6)/2) * 13^(1/4) / (2^(13/4) * 3^(1/4) * n^(3/4)) * (1 -(3*sqrt(3)/(2*Pi*sqrt(26)) + Pi*sqrt(13)/(96*sqrt(6)))/sqrt(n) + (13*Pi^2/110592 - 45/(208*Pi^2) + 5/128)/n).

A233006 Expansion of psi(x) / f(-x^6) in powers of x where psi(), f() are Ramanujan theta functions.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 2, 1, 0, 1, 1, 0, 3, 2, 0, 3, 1, 0, 5, 3, 0, 5, 2, 0, 8, 5, 0, 8, 4, 0, 12, 7, 0, 12, 6, 0, 19, 11, 0, 19, 9, 0, 27, 15, 0, 28, 14, 0, 39, 22, 0, 41, 20, 0, 55, 31, 0, 58, 29, 0, 77, 43, 0, 82, 41, 0, 106, 58, 0, 113, 57, 0, 145, 80, 0, 156
Offset: 0

Views

Author

Michael Somos, Dec 03 2013

Keywords

Comments

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

Examples

			G.f. = 1 + x + x^3 + 2*x^6 + x^7 + x^9 + x^10 + 3*x^12 + 2*x^13 + 3*x^15 + ...
G.f. = q + q^9 + q^25 + 2*q^49 + q^57 + q^73 + q^81 + 3*q^97 + 2*q^105 + ...
		

Crossrefs

Programs

  • Mathematica
    a[ n_] := SeriesCoefficient[ EllipticTheta[ 2, 0, x^(1/2)] / (2 x^(1/8) QPochhammer[ x^6]), {x, 0, n}];
  • PARI
    {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^2 + A)^2 / (eta(x + A) * eta(x^6 + A)), n))};

Formula

Expansion of q^(-1/8) * eta(q^2)^2 / (eta(q) * eta(q^6)) in powers of q.
Euler transform of period 6 sequence [ 1, -1, 1, -1, 1, 0, ...].
G.f. is a period 1 Fourier series which satisfies f(-1 / (1152 t)) = (3/2)^(1/2) g(t) where q = exp(2 Pi i t) and g() is the g.f. of A070047.
G.f.: Product_{k>0} (1 + x^k) / (1 + x^(2*k) + x^(4*k)).
a(3*n) = A070047(n). a(3*n + 1) = A097451(n). a(3*n + 2) = 0.

A294199 Number of partitions of n into powers of 2 such that 1 and 2 cannot both be parts of a particular partition, and 4 and 8 cannot both be parts of a particular partition, and 16 and 32, and so on.

Original entry on oeis.org

1, 1, 2, 1, 3, 2, 4, 2, 6, 4, 8, 4, 9, 5, 10, 5, 13, 8, 16, 8, 18, 10, 20, 10, 24, 14, 28, 14, 30, 16, 32, 16, 38, 22, 44, 22, 48, 26, 52, 26, 60, 34, 68, 34, 72, 38, 76, 38, 85, 47, 94, 47, 99, 52, 104, 52, 114, 62, 124, 62, 129, 67, 134, 67, 147, 80, 160
Offset: 0

Views

Author

Vaclav Kotesovec, Oct 24 2017

Keywords

Examples

			a(10) = 8 where the partitions are the following: 8+2, 8+1+1, 4+4+2, 4+2+2+2, 4+4+1+1, 4+1+1+1+1+1+1, 2+2+2+2+2, 1+1+1+1+1+1+1+1+1+1.
		

Crossrefs

Cf. A070047.

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Product[(1-x^(3*2^(2*k-2)))/(1-x^(2^(k-1))), {k, 1, nmax}], {x, 0, nmax}], x]
    a[0] = 1; a[1] = 1; a[2] = 2; a[3] = 1; Flatten[{1, 1, 2, 1, Table[If[EvenQ[n], a[n] = a[n-2] + a[Floor[n/4]], a[n] = a[n-1] - a[n-2]], {n, 4, 100}]}]

Formula

G.f.: Product_{k>=1} (1 - x^(2^(2*k-2) + 2^(2*k-1))) / ((1 - x^(2^(2*k-2))) * (1 - x^(2^(2*k-1)))).
G.f.: Product_{k>=1} (1 - x^(3*2^(2*k-2))) / (1 - x^(2^(k-1))).
For n>=1 a(2*n) = a(2*n-2) + a([n/2]).
For n>=1 a(2*n+1) = a(2*n) - a(2*n-1).
Showing 1-8 of 8 results.