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 1-5 of 5 results.

A370716 a(n) = 3^(2*n) * [x^n] Product_{k>=1} (1 + 2*x^k)^(1/3).

Original entry on oeis.org

1, 6, 18, 1170, -1890, 133326, 101250, 20498994, -164656314, 3778220862, -28085954094, 771567716970, -10691904063114, 183594050113518, -2711145260068326, 49416883617381354, -789899109743435994, 13176840267952166070, -216403389726994588086, 3681309971143060236810
Offset: 0

Views

Author

Vaclav Kotesovec, Feb 27 2024

Keywords

Crossrefs

Cf. A032302, A370715.
Cf. A075900, A300581, A304961, A327550.

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Product[(1 + 2*x^k), {k, 1, nmax}]^(1/3), {x, 0, nmax}], x] * 3^(2*Range[0, nmax])
nmax = 20; CoefficientList[Series[Product[(1 + 2*(9*x)^k), {k, 1, nmax}]^(1/3), {x, 0, nmax}], x]
nmax = 20; CoefficientList[Series[(QPochhammer[-2, x]/3)^(1/3), {x, 0, nmax}], x] * 3^(2*Range[0, nmax])

Formula

G.f.: Product_{k>=1} (1 + 2*(9*x)^k)^(1/3).
a(n) ~ (-1)^(n+1) * c * 18^n / n^(4/3), where c = QPochhammer(-1/2)^(1/3) / (3*Gamma(2/3)) = 0.2623638446186535909018671540030519...

A370732 a(n) = 4^n * [x^n] Product_{k>=1} 1/(1 - 2*x^k)^(1/4).

Original entry on oeis.org

1, 2, 18, 108, 822, 4796, 37492, 231704, 1738150, 11857004, 87262684, 617409128, 4638712124, 33724007896, 253800160808, 1894353653552, 14350905612038, 108412437326412, 827441075006796, 6308125533133896, 48388714839180756, 371391625244862600, 2860885559165073624
Offset: 0

Views

Author

Vaclav Kotesovec, Feb 28 2024

Keywords

Crossrefs

Cf. A070933 (m=1), A370713 (m=2), A370715 (m=3), A370733 (m=5).

Programs

  • Mathematica
    nmax = 30; CoefficientList[Series[Product[1/(1-2*x^k), {k, 1, nmax}]^(1/4), {x, 0, nmax}], x] * 4^Range[0, nmax]
nmax = 30; CoefficientList[Series[Product[1/(1-2*(4*x)^k), {k, 1, nmax}]^(1/4), {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} 1/(1 - 2*(4*x)^k)^(1/4).
a(n) ~ 8^n / (Gamma(1/4) * QPochhammer(1/2)^(1/4) * n^(3/4)).

A370735 a(n) = 5^(2*n) * [x^n] Product_{k>=1} 1/(1 - 3*x^k)^(1/5).

Original entry on oeis.org

1, 15, 1050, 52125, 3277500, 179801250, 11966690625, 738318187500, 49788716718750, 3314446448437500, 227432073022265625, 15631633385109375000, 1090877899335878906250, 76338563689129101562500, 5384934139819611328125000, 381204340327212964599609375, 27111589537137988341064453125
Offset: 0

Views

Author

Vaclav Kotesovec, Feb 28 2024

Keywords

Comments

In general, if d > 1, m >= 1 and g.f. = Product_{k>=1} 1/(1 - d*x^k)^(1/m), then a(n) ~ d^n / (Gamma(1/m) * QPochhammer(1/d)^(1/m) * n^(1 - 1/m)).

Crossrefs

Cf. A242587 (d=3,m=1), A370714 (d=3,m=2), A370710 (d=3,m=3), A370734 (d=3,m=4).
Cf. A070933 (d=2,m=1), A370713 (d=2,m=2), A370715 (d=2,m=3), A370732 (d=2,m=4), A370733 (d=2,m=5).
Cf. A000041 (d=1,m=1), A271235 (d=1,m=2), A271236 (d=1,m=3).

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Product[1/(1-3*x^k), {k, 1, nmax}]^(1/5), {x, 0, nmax}], x] * 25^Range[0, nmax]
nmax = 20; CoefficientList[Series[Product[1/(1-3*(25*x)^k), {k, 1, nmax}]^(1/5), {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} 1/(1 - 3*(25*x)^k)^(1/5).
a(n) ~ 75^n / (Gamma(1/5) * QPochhammer(1/3)^(1/5) * n^(4/5)).

A370733 a(n) = 5^(2*n) * [x^n] Product_{k>=1} 1/(1 - 2*x^k)^(1/5).

Original entry on oeis.org

1, 10, 550, 19750, 921250, 32011250, 1563143750, 58080093750, 2719958906250, 113913469531250, 5214823539843750, 228024893230468750, 10704801509316406250, 482674223446582031250, 22664252188144042968750, 1053427002068999511718750, 49776941230938518066406250
Offset: 0

Views

Author

Vaclav Kotesovec, Feb 28 2024

Keywords

Crossrefs

Cf. A070933 (m=1), A370713 (m=2), A370715 (m=3), A370732 (m=4).

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Product[1/(1-2*x^k), {k, 1, nmax}]^(1/5), {x, 0, nmax}], x] * 25^Range[0, nmax]
nmax = 20; CoefficientList[Series[Product[1/(1-2*(25*x)^k), {k, 1, nmax}]^(1/5), {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} 1/(1 - 2*(25*x)^k)^(1/5).
a(n) ~ 50^n / (Gamma(1/5) * QPochhammer(1/2)^(1/5) * n^(4/5)).

A370750 a(n) = 9^n * [x^n] Product_{k>=1} ((1 + 2*x^k)/(1 - 2*x^k))^(1/3).

Original entry on oeis.org

1, 12, 180, 3852, 50436, 947052, 14087844, 245858652, 3531115620, 64019229660, 950199749748, 16959724619004, 256888616329044, 4642974930688812, 71716402072904724, 1308491345357401068, 20501966472318764388, 376230182366985289164, 5987314157007778195716, 110286515004790197907836
Offset: 0

Views

Author

Vaclav Kotesovec, Feb 29 2024

Keywords

Crossrefs

Cf. A261584, A303346, A370749.
Cf. A032302, A070933.
Cf. A370716, A370715.

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Product[(1 + 2*x^k)/(1 - 2*x^k), {k, 1, nmax}]^(1/3), {x, 0, nmax}], x] * 9^Range[0, nmax]
nmax = 20; CoefficientList[Series[Product[(1 + 2*(9*x)^k)/(1 - 2*(9*x)^k), {k, 1, nmax}]^(1/3), {x, 0, nmax}], x]

Formula

G.f.: Product_{k>=1} ((1 + 2*(9*x)^k)/(1 - 2*(9*x)^k))^(1/3).
a(n) ~ QPochhammer(-1, 1/2)^(1/3) * 18^n / (Gamma(1/3) * QPochhammer(1/2)^(1/3) * n^(2/3)).
Showing 1-5 of 5 results.

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