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.

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A338046 G.f.: Sum_{k>=0} x^(2^k) / (1 - x^(2^k))^4.

Original entry on oeis.org

1, 5, 10, 25, 35, 66, 84, 145, 165, 255, 286, 430, 455, 644, 680, 961, 969, 1305, 1330, 1795, 1771, 2310, 2300, 3030, 2925, 3731, 3654, 4704, 4495, 5640, 5456, 6945, 6545, 8109, 7770, 9741, 9139, 11210, 10660, 13275, 12341, 15015, 14190, 17490, 16215, 19596, 18424, 22630
Offset: 1

Views

Author

Ilya Gutkovskiy, Oct 08 2020

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 48; CoefficientList[Series[Sum[x^(2^k) /(1 - x^(2^k))^4, {k, 0, Floor[Log[2, nmax]] + 1}], {x, 0, nmax}], x] // Rest
    a[n_] := If[EvenQ[n], a[n/2] + n (n + 1) (n + 2)/6, n (n + 1) (n + 2)/6]; Table[a[n], {n, 1, 48}]
    Table[(1/6) DivisorSum[n, Boole[IntegerQ[Log[2, n/#]]] # (# + 1) (# + 2) &], {n, 1, 48}]

Formula

G.f. A(x) satisfies: A(x) = A(x^2) + x / (1 - x)^4.
a(2*n) = a(n) + A002492(n), a(2*n+1) = A000447(n+1).
a(n) = (1/6) * Sum_{d|n} A209229(n/d) * d * (d + 1) * (d + 2).
Product_{n>=1} (1 + x^n)^a(n) = g.f. for A000335.

A279761 Expansion of Product_{k>=1} 1/(1 - x^k)^(k*(2*k^2+1)/3).

Original entry on oeis.org

1, 1, 7, 26, 91, 290, 946, 2922, 8937, 26521, 77485, 222005, 626988, 1743739, 4787625, 12979799, 34792728, 92257673, 242197348, 629805075, 1623197726, 4148192991, 10516418844, 26458470616, 66086152465, 163925621199, 403931474096, 989040788801, 2407020523315, 5823830868091, 14011949899801, 33530477120905, 79820957945103
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 18 2016

Keywords

Comments

Euler transform of the octahedral numbers (A005900).

Crossrefs

Programs

  • Mathematica
    nmax=32; CoefficientList[Series[Product[1/(1 - x^k)^(k (2 k^2 + 1)/3), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} 1/(1 - x^k)^(k*(2*k^2+1)/3).
a(n) ~ exp(Zeta'(-1)/3 - Zeta(3)^2 / (360*Zeta(5)) + 2*Zeta'(-3)/3 + (Zeta(3)/(6*2^(3/5) * Zeta(5)^(2/5))) * n^(2/5) + (5*(Zeta(5)/2)^(1/5)/2) * n^(4/5)) * Zeta(5)^(47/450) / (2^(37/450) * sqrt(5*Pi) * n^(136/225)). - Vaclav Kotesovec, Nov 09 2017

A279762 Expansion of Product_{k>=1} 1/(1 - x^k)^(k*(5*k^2-5*k+2)/2).

Original entry on oeis.org

1, 1, 13, 61, 263, 1094, 4578, 18076, 69815, 262242, 965342, 3480006, 12322360, 42896002, 147062818, 497000146, 1657470977, 5459160063, 17772284155, 57225458626, 182362100816, 575463112191, 1799106136923, 5575063264825, 17130798464652, 52216240087807, 157937816918539, 474197830869573, 1413695306175884, 4185962563381518
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 18 2016

Keywords

Comments

Euler transform of the icosahedral numbers (A006564).

Crossrefs

Programs

  • Mathematica
    nmax=29; CoefficientList[Series[Product[1/(1 - x^k)^(k (5 k^2 - 5 k + 2)/2), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} 1/(1 - x^k)^(k*(5*k^2-5*k+2)/2).
a(n) ~ exp(Zeta'(-1) + 5*Zeta(3) / (8*Pi^2) - Pi^16 / (16796160000*Zeta(5)^3) + Pi^8 * Zeta(3) / (648000*Zeta(5)^2) - Zeta(3)^2 / (150*Zeta(5)) + 5*Zeta'(-3)/2 + (-Pi^12/(19440000 * 2^(2/5) * 15^(1/5) * Zeta(5)^(11/5)) + Pi^4 * Zeta(3) / (900 * 2^(2/5) * 15^(1/5) * Zeta(5)^(6/5))) * n^(1/5) + (-Pi^8 / (21600 * 2^(4/5) * 15^(2/5) * Zeta(5)^(7/5)) + Zeta(3) / (2^(4/5) * (15*Zeta(5))^(2/5))) * n^(2/5) + (-Pi^4 / (36 * 2^(1/5) * (15*Zeta(5))^(3/5))) * n^(3/5) + ((5*(15*Zeta(5))^(1/5)) / 2^(8/5)) * n^(4/5)) * (3*Zeta(5))^(9/80) / (2^(11/40) * 5^(31/80) * sqrt(Pi) * n^(49/80)). - Vaclav Kotesovec, Nov 09 2017

A279763 Expansion of Product_{k>=1} 1/(1 - x^k)^(k*(3*k-1)*(3*k-2)/2).

Original entry on oeis.org

1, 1, 21, 105, 535, 2670, 12996, 59546, 266875, 1161894, 4939778, 20528320, 83636061, 334496221, 1315381029, 5091782355, 19424086781, 73092029218, 271537720562, 996656173345, 3616680935702, 12983391870459, 46133749660407, 162337625047433, 565962994479384, 1955721907216420, 6701061533668542, 22774651422340672
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 18 2016

Keywords

Comments

Euler transform of the dodecahedral numbers (A006566).

Crossrefs

Programs

  • Mathematica
    nmax=27; CoefficientList[Series[Product[1/(1 - x^k)^(k (3 k - 1) (3 k - 2)/2), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} 1/(1 - x^k)^(k*(3*k-1)*(3*k-2)/2).
a(n) ~ exp(Zeta'(-1) + 9*Zeta(3) / (8*Pi^2) - Pi^16 / (9331200000*Zeta(5)^3) + Pi^8 * Zeta(3) / (648000*Zeta(5)^2) - Zeta(3)^2 / (270*Zeta(5)) + 9*Zeta'(-3)/2 + (-Pi^12/(10800000 * 2^(2/5) * 3^(3/5) * Zeta(5)^(11/5)) + Pi^4 * Zeta(3) / (900 * 2^(2/5) * 3^(3/5) * Zeta(5)^(6/5))) * n^(1/5) + (-Pi^8 / (36000 * 2^(4/5) * 3^(1/5) * Zeta(5)^(7/5)) + Zeta(3) / (2^(4/5) * 3^(6/5) * Zeta(5)^(2/5))) * n^(2/5) + (-Pi^4 / (60 * 2^(1/5) * 3^(4/5) * Zeta(5)^(3/5))) * n^(3/5) + ((5*3^(3/5) * Zeta(5)^(1/5)) / 2^(8/5)) * n^(4/5)) * 3^(131/400) * Zeta(5)^(131/1200) / (2^(169/600) * sqrt(5*Pi) * n^(731/1200)). - Vaclav Kotesovec, Nov 09 2017
Previous Showing 31-34 of 34 results.