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 1-7 of 7 results.

A302583 a(n) = ((n + 1)^n - (n - 1)^n)/2.

Original entry on oeis.org

0, 1, 4, 28, 272, 3376, 51012, 908608, 18640960, 432891136, 11225320100, 321504185344, 10079828372880, 343360783937536, 12627774819845668, 498676704524517376, 21046391759976988928, 945381827279671853056, 45032132922921758270916, 2267322327322331161821184
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 10 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[((n + 1)^n - (n - 1)^n)/2, {n, 0, 19}]
    nmax = 19; CoefficientList[Series[(x^2 - LambertW[-x]^2)/(2 x LambertW[-x] (1 + LambertW[-x])), {x, 0, nmax}], x] Range[0, nmax]!
    Table[n! SeriesCoefficient[Exp[n x] Sinh[x], {x, 0, n}], {n, 0, 19}]

Formula

E.g.f.: (x^2 - LambertW(-x)^2)/(2*x*LambertW(-x)*(1 + LambertW(-x))).
a(n) = n! * [x^n] exp(n*x)*sinh(x).

A115415 Real part of (n + i)^n, with i=sqrt(-1).

Original entry on oeis.org

1, 1, 3, 18, 161, 1900, 27755, 482552, 9722113, 222612624, 5707904499, 161981127968, 5039646554593, 170561613679808, 6237995487261915, 245159013138710400, 10303367499652761601, 461102348510408544512, 21891769059478538933603, 1098983344602124698522112
Offset: 0

Views

Author

Reinhard Zumkeller, Jan 22 2006

Keywords

Crossrefs

Cf. A000312, A009545, A115416 (imaginary part), A121626, A370189.

Programs

  • Mathematica
    Table[ Re[(n + I)^n], {n, 0, 17}] (* Robert G. Wilson v, Jan 23 2006 *)
  • PARI
    a(n) = real((n + I)^n); \\ Michel Marcus, Apr 11 2018
    
  • Python
    from math import comb
    def A115415(n): return sum(comb(n,j)*n**(n-j)*(-1 if j&2 else 1) for j in range(0,n+1,2)) # Chai Wah Wu, Feb 15 2024

Formula

a(n) = n! * [x^n] exp(n*x)*cos(x). - Ilya Gutkovskiy, Apr 10 2018
a(n) ~ cos(1) * n^n. - Vaclav Kotesovec, Jun 08 2019
a(n) = Sum_{j=0..floor(n/2)} binomial(n,2j)*n^(n-2j)*(-1)^j. - Chai Wah Wu, Feb 15 2024
a(n) = (1/2)*((n + i)^n + (n - i)^n) where i is the imaginary unit. - Gerry Martens, Dec 30 2024

Extensions

More terms from Robert G. Wilson v, Jan 23 2006

A302584 a(n) = n! * [x^n] exp(n*x)/cos(x).

Original entry on oeis.org

1, 1, 5, 36, 357, 4500, 68857, 1239504, 25661545, 600655824, 15684383021, 452001644864, 14249852124365, 487836995500608, 18022519535240417, 714658089577017600, 30275849571771536977, 1364687729891761740032, 65213822241378992547925, 3293203845745202062590976
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 10 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[n x]/Cos[x], {x, 0, n}], {n, 0, 19}]
    Table[(2 I)^n EulerE[n, (1 - I n)/2], {n, 0, 19}]

Formula

a(n) ~ n^n / cos(1). - Vaclav Kotesovec, Jun 08 2019

A302586 a(n) = n! * [x^n] exp(n*x)*tan(x).

Original entry on oeis.org

0, 1, 4, 29, 288, 3641, 55872, 1008349, 20923392, 490730641, 12836633600, 370512824285, 11697136754688, 400947361714121, 14829211483455488, 588633245015433437, 24960134277040177152, 1126038686507284428961, 53851620649898789830656, 2721385807644104827095965
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 10 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[n x] Tan[x], {x, 0, n}], {n, 0, 19}]
    Table[I^(n + 1) 2^(n - 1) (EulerE[n, (-I/2) n] - EulerE[n, 1 - (I/2) n]), {n, 0, 19}]

Formula

a(n) ~ tan(1) * n^n. - Vaclav Kotesovec, Jun 08 2019

A302605 a(n) = n! * [x^n] exp(n*x)*arcsin(x).

Original entry on oeis.org

0, 1, 4, 28, 272, 3384, 51300, 917064, 18884672, 440168832, 11454902500, 329208395264, 10355322975120, 353851897861760, 13052503620917124, 516917167506777600, 21875427250996723968, 985164766018898243584, 47043119138733155306052, 2374168079889664129576960
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 10 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[n x] ArcSin[x], {x, 0, n}], {n, 0, 19}]

Formula

a(n) = Sum_{k=1..n} binomial(n,k)*(k-2)!!^2*n^(n-k)*(1-(-1)^k)/2. - Fabian Pereyra, Oct 05 2024

A370189 Imaginary part of (1 + n*i)^n, where i is the imaginary unit.

Original entry on oeis.org

0, 1, 4, -18, -240, 1900, 42372, -482552, -14970816, 222612624, 8825080100, -161981127968, -7809130867824, 170561613679808, 9678967816041188, -245159013138710400, -16000787866533953280, 461102348510408544512, 34017524842099233036996, -1098983344602124698522112, -90417110945911655996319600
Offset: 0

Views

Author

Hugo Pfoertner, Feb 14 2024

Keywords

Comments

The ratio a(n)/A121626(n) converges to c for odd n and to -1/c for even n for n -> oo with c = 0.6420926... (= cot(1) (A073449) from Moritz Firsching, Feb 14 2024). See linked plots.

Crossrefs

Cf. A121626 (real part), A115415, A115416.
Cf. A073449.

Programs

  • Mathematica
    Array[Im[(1+#*I)^#] &, 25, 0] (* Paolo Xausa, Feb 19 2024 *)
  • PARI
    a370189(n) = imag((1+I*n)^n)
    
  • Python
    from math import comb
    def A370189(n): return sum(comb(n,j)*n**j*(-1 if j-1&2 else 1) for j in range(1,n+1,2)) # Chai Wah Wu, Feb 15 2024

Formula

a(n) = Sum_{j=0..floor((n-1)/2)} binomial(n,2*j+1)*n^(2*j+1)*(-1)^j. - Chai Wah Wu, Feb 15 2024

A176302 a(n) = floor(abs( (i+n)^n )) where "i" is the Imaginary unit.

Original entry on oeis.org

1, 5, 31, 289, 3446, 50653, 883883, 17850625, 409413666, 10510100501, 298523873866, 9294114390625, 314715395761089, 11514990476898413, 452702917746710142, 19031147999601100801, 851888944448164153708
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Magma
    C := ComplexField(); [Floor(Abs( (n+I)^n )): n in [1..30]]; // G. C. Greubel, Nov 26 2019
    
  • Maple
    seq(floor(abs((n+I)^n)), n = 1..30); # G. C. Greubel, Nov 26 2019
  • Mathematica
    Table[Floor@Abs[(I + n)^n], {n,30}]
  • PARI
    default(realprecision, 50); vector(30, n, (abs((I+n)^n))\1 ) \\ G. C. Greubel, Nov 26 2019
    
  • Sage
    [floor(abs( (n+i)^n )) for n in (1..30)] # G. C. Greubel, Nov 26 2019
Showing 1-7 of 7 results.