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

A123854 Denominators in an asymptotic expansion for the cubic recurrence sequence A123851.

Original entry on oeis.org

1, 4, 32, 128, 2048, 8192, 65536, 262144, 8388608, 33554432, 268435456, 1073741824, 17179869184, 68719476736, 549755813888, 2199023255552, 140737488355328, 562949953421312, 4503599627370496, 18014398509481984, 288230376151711744, 1152921504606846976
Offset: 0

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Author

Keywords

Comments

A cubic analog of the asymptotic expansion A116603 of Somos's quadratic recurrence sequence A052129. Numerators are A123853.
Equals 2^A004134(n); also the denominators in expansion of (1-x)^(-1/4). - Alexander Adamchuk, Oct 27 2006
All terms are powers of 2 and log_2 a(n) = A004134(n) = 3*n - A000120(n). - Alexander Adamchuk, Oct 27 2006 [Edited by Petros Hadjicostas, May 14 2020]
Is this the same sequence as A088802? - N. J. A. Sloane, Mar 21 2007
Almost certainly this is the same as A088802. - Michael Somos, Aug 23 2007
Denominators of Gegenbauer_C(2n,1/4,2). The denominators of Gegenbauer_C(n,1/4,2) give the doubled sequence. - Paul Barry, Apr 21 2009
If the Greubel formula in A088802 and the Luschny formula here are correct (they are the same), the sequence is a duplicate of A088802. - R. J. Mathar, Aug 02 2023

Examples

			A123851(n) ~ c^(3^n)*n^(- 1/2)/(1 + 3/(4*n) - 15/(32*n^2) + 113/(128*n^3) - 5397/(2048*n^4) + ...) where c = 1.1563626843322... is the cubic recurrence constant A123852.
		

References

  • Steven R. Finch, Mathematical Constants, Cambridge University Press, Cambridge, 2003, p. 446.

Crossrefs

Programs

  • Maple
    f:=proc(t,x) exp(sum(ln(1+m*x)/t^m,m=1..infinity)); end; for j from 0 to 29 do denom(coeff(series(f(3,x),x=0,30),x,j)); od;
    # Alternatively:
    A123854 := n -> denom(binomial(1/4,n)):
    seq(A123854(n), n=0..25); # Peter Luschny, Apr 07 2016
  • Mathematica
    Denominator[CoefficientList[Series[ 1/Sqrt[Sqrt[1-x]], {x, 0, 25}], x]] (* Robert G. Wilson v, Mar 23 2014 *)
  • PARI
    vector(25, n, n--; denominator(binomial(1/4,n)) ) \\ G. C. Greubel, Aug 08 2019
  • Sage
    # uses[A000120]
    def A123854(n): return 1 << (3*n-A000120(n))
    [A123854(n) for n in (0..25)]  # Peter Luschny, Dec 02 2012
    

Formula

From Alexander Adamchuk, Oct 27 2006: (Start)
a(n) = 2^A004134(n).
a(n) = 2^(3n - A000120(n)). (End)
a(n) = denominator(binomial(1/4,n)). - Peter Luschny, Apr 07 2016

A004130 Numerators in expansion of (1-x)^{-1/4}.

Original entry on oeis.org

1, 1, 5, 15, 195, 663, 4641, 16575, 480675, 1762475, 13042315, 48612265, 729183975, 2748462675, 20809788825, 79077197535, 4823709049635, 18443593425075, 141400882925575, 543277076503525, 8366466978154285, 32270658344309385
Offset: 0

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Keywords

Comments

Numerators in expansion of sqrt(1/sqrt(1-4x)). - Paul Barry, Jul 12 2005
Denominators are in A088802. - Michael Somos, Aug 23 2007

Crossrefs

Programs

  • Mathematica
    Table[Numerator[Binomial[-1/4, n] (-1)^n], {n, 0, 20}]
  • PARI
    {a(n) = if( n<0, 0, numerator( polcoeff( (1 - x +x*O(x^n))^(-1/4), n ) ) ) } /* Michael Somos, Aug 23 2007 */

Formula

a(n) = prod(k=1, n, (4k-3)/k * 2^A007814(k)), proved by Mitch Harris, following a conjecture by Ralf Stephan.
a(n) = 2^(e_2((2n)!)-n)/n! Product[4k+1,{k,0,n-1}], where e_2((2n)!) is the highest power of 2 that divides (2n)! (sequence A005187). - Emanuele Munarini, Jan 25 2011
Numerators in (1-4t)^(-1/4) = 1 + t + (5/2)t^2 + (15/2)t^3 + (195/8)t^4 + (663/8)t^5 + (4641/16)t^6 + (16575/16)t^7 + ... = 1 + t + 5*t^2/2! + 45*t^3/3! + 585*t^4/4! + ... = e.g.f. for the quartic factorials A007696 (cf. A094638). - Tom Copeland, Dec 04 2013

A006934 A series for Pi.

Original entry on oeis.org

1, 1, 21, 671, 180323, 20898423, 7426362705, 1874409467055, 5099063967524835, 2246777786836681835, 2490122296790918386363, 1694873049836486741425113, 5559749161756484280905626951, 5406810236613380495234085140851, 12304442295910538475633061651918089
Offset: 0

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Author

Keywords

Comments

Formula (21) in Luke (see ref.): Let y = 4*n+1. Then for n -> oo
Pi ~ 4*(n!)^4*2^(4*n)/(y*((2*n)!)^2)*(sum_{k>=0}((-1)^k*y^(-2*k)* A006934(k)/A123854(k)))^2. (Luke does not reference the sequences in this form.) - Peter Luschny, Mar 23 2014
This might be related to the numerators of eq. (18) in N. Elezovic' "Asymptotic Expansions of Central Binomial...", J. Int. Seq. 17 (2014) # 14.2.1. - R. J. Mathar, Mar 23 2014
Several references give an erroneous value of 1874409465055 instead of a(7) in the formula for pi. - M. F. Hasler, Mar 23 2014

References

  • Y. L. Luke, The Special Functions and their Approximation, Vol. 1, Academic Press, NY, 1969, see p. 36.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Maple
    A006934_list := proc(n) local k, f, bp;
    bp := proc(n,x) option remember; local k; if n = 0 then 1 else -x*add(binomial(n-1,2*k+1)*bernoulli(2*k+2)/(k+1)*bp(n-2*k-2,x), k=0..n/2-1) fi end:
    f := n -> 2^(3*n-add(i, i=convert(n,base,2)));
    add(bp(2*k,1/4)*binomial(4*k,2*k)*x^(2*k), k=0..n-1);
    seq((-1)^k*f(k)*coeff(%,x,2*k), k=0..n-1) end:
    A006934_list(15);  # Peter Luschny, Mar 23 2014
    # Second solution, without using Nörlund's generalized Bernoulli polynomials, based on Euler numbers:
    A006934_list := proc(n) local a,c,j;
    c := n -> 4^n/2^add(i, i=convert(n,base,2));
    a := [seq((-4)^j*euler(2*j)/(4*j), j=1..n)];
    expand(exp(add(a[j]*x^(-j), j=1..n))); taylor(%, x=infinity, n+2);
    subs(x=1/x, convert(%,polynom)): seq(c(iquo(j,2))*coeff(%,x,j), j=0..n) end:
    A006934_list(14); # Peter Luschny, Apr 08 2014
  • Mathematica
    A006934List[n_] := Module[{c, a, s, sx}, c[k_] := 4^k/2^Total[ IntegerDigits[k, 2]]; a = Table[(-4)^j EulerE[2j]/(4j), {j, 1, n}]; s[x_] = Series[Exp[Sum[a[[j]] x^(-j), {j, 1, n}]], {x, Infinity, n+2}] // Normal; sx = s[1/x]; Table[c[Quotient[j, 2]] Coefficient[sx, x, j], {j, 0, n}]];
    A006934List[14] (* Jean-François Alcover, Jun 02 2019, from second Maple program *)
  • Sage
    @CachedFunction
    def p(n):
        if n < 2: return 1
        return -add(binomial(n-1,k-1)*bernoulli(k)*p(n-k)/k for k in range(2,n+1,2))/2
    def A006934(n): return (-1)^n*p(2*n)*binomial(4*n,2*n)*2^(3*n-sum(n.digits(2)))
    [A006934(n) for n in (0..14)]  # Peter Luschny, Mar 24 2014

Formula

Let p(n,x) = sum(k=0..n, x^k*A220412(n,k))/A220411(n) then a(n) = (-1)^n*p(n,1/4)*A123854(n)*A001448(n). - Peter Luschny, Mar 23 2014
Pi = lim_{n->oo} 2^{4n+2}/((4n+1)*C(2n,n)^2)*(sum_{k=0..oo} (-1)^k*a(k)/(A123854(k)*(4n+1)^{2k}))^2. - M. F. Hasler, Mar 23 2014

Extensions

a(7) corrected, a(8)-a(14) from Peter Luschny, Mar 23 2014

A126963 Numerators of sequence defined by f(0)=1, f(1)=5/4; f(n) = ( (6*n-1)*f(n-1) - (2*n-1)*f(n-2) )/(4n).

Original entry on oeis.org

1, 5, 43, 177, 2867, 11531, 92479, 370345, 11857475, 47442055, 379582629, 1518418695, 24295375159, 97182800711, 777467420263, 3109879375897, 199032580597603, 796130905791967, 6369049515119561, 25476202478636219, 407619274119811709, 1630477163761481141
Offset: 0

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Author

N. J. A. Sloane, Mar 20 2007

Keywords

Crossrefs

Denominators are in A088802.

Programs

  • GAP
    List([0..25], n-> NumeratorRat( Sum([0..n], k-> Binomial(2*k,k)/8^k) ));  # G. C. Greubel, Jan 29 2020
  • Magma
    [Numerator( &+[Binomial(2*k, k)/8^k: k in [0..n]] ): n in [0..25]]; // G. C. Greubel, Jan 29 2020
    
  • Maple
    seq( numer( add(binomial(2*k, k)/8^k, k=0..n) ), n=0..25); # G. C. Greubel, Jan 29 2020
  • Mathematica
    a[n_] := Sqrt[2](1-(Gamma[1/2+n] Hypergeometric2F1[n,1/2+n,1+n,-1])/(Sqrt[Pi] Gamma[1+n])); Table[Numerator[FullSimplify[a[n]]], {n,20}] (* Gerry Martens, Aug 09 2015 *)
    f[n_]:= If[n==0, 1, If[n==1, 5/4, ((6*n-1)*f[n-1]-(2*n-1)*f[n-2])/(4*n)]];
    Table[Numerator[f[n]], {n, 0, 25}] (* G. C. Greubel, Jan 29 2020 *)
  • PARI
    A126963(n)=numerator(sum(k=0,n,binomial(-1/2,k)/(-2)^k)) \\ f(n)=if(n>1,((6*n-1)*f(n-1)-(2*n-1)*f(n-2))/(4*n),(5/4)^n) yields the same results. - M. F. Hasler, Aug 11 2015
    
  • Sage
    [numerator( sum(binomial(2*k, k)/8^k for k in (0..n)) ) for n in (0..25)] # G. C. Greubel, Jan 29 2020
    

Formula

f(n) = Sum_{k=0..n} binomial(-1/2,k)*(-1/2)^k.
f(n) -> sqrt(2) as n -> oo.
G.f.: (sqrt(-x)*arccsc(1-x)/sqrt(2)-(Pi*i*sqrt(x))/sqrt(2)^3)/x. - Vladimir Kruchinin, Oct 10 2012
a(n) = numerator( Sum_{k=0..n} binomial(2*k, k)/8^k ). - G. C. Greubel, Jan 29 2020

A143503 Numerators in the asymptotic expansion of Gamma(x+1/2)/Gamma(x).

Original entry on oeis.org

1, -1, 1, 5, -21, -399, 869, 39325, -334477, -28717403, 59697183, 8400372435, -34429291905, -7199255611995, 14631594576045, 4251206967062925, -68787420596367165, -26475975382085110035, 53392138323683746235, 26275374869163335461975, -105772979046693606062363
Offset: 1

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Author

Eric W. Weisstein, Aug 20 2008

Keywords

Examples

			1/sqrt(x^(-1)) - sqrt(x^(-1))/8 + (x^(-1))^(3/2)/128 + (5*(x^(-1))^(5/2))/1024 - (21*(x^(-1))^(7/2))/32768 + ...
		

Crossrefs

Cf. A061549, A088802 (denominators), A222411, A222412.

Programs

  • Maple
    H := proc(n) local S, i; S := (x/(exp(x)-1))^(3/2)*exp(x/2);
    -pochhammer(1/2,n-1)*coeff(series(S,x,n+2),x,n)*2^(4*n-1-add(i,i= convert(n,base,2))) end:
    A143503 := n -> (-1)^irem(n-1,6)*H(n-1);
    seq(A143503(n), n=1..16); # Peter Luschny, Apr 05 2014
  • Mathematica
    Numerator[CoefficientList[Series[Gamma[x + 1/2]/Gamma[x]/Sqrt[x], {x, Infinity, 20}], 1/x]] (* Vaclav Kotesovec, Oct 09 2023 *)

Extensions

More terms from Vaclav Kotesovec, Oct 09 2023

A348678 Triangle read by rows, T(n, k) = denominator([x^k] M(n, x)) where M(n,x) are the Mandelbrot-Larsen polynomials defined in A347928.

Original entry on oeis.org

1, 1, 2, 1, 4, 8, 1, 1, 8, 16, 1, 8, 32, 32, 128, 1, 1, 16, 64, 64, 256, 1, 1, 32, 128, 256, 512, 1024, 1, 1, 1, 64, 256, 512, 1024, 2048, 1, 16, 128, 256, 2048, 64, 4096, 4096, 32768, 1, 1, 32, 256, 512, 4096, 1024, 8192, 8192, 65536
Offset: 0

Views

Author

Peter Luschny, Oct 29 2021

Keywords

Examples

			Triangle starts:
[0] 1
[1] 1,  2
[2] 1,  4,   8
[3] 1,  1,   8,  16
[4] 1,  8,  32,  32,  128
[5] 1,  1,  16,  64,   64,  256
[6] 1,  1,  32, 128,  256,  512, 1024
[7] 1,  1,   1,  64,  256,  512, 1024, 2048
[8] 1, 16, 128, 256, 2048,   64, 4096, 4096, 32768
[9] 1,  1,  32, 256,  512, 4096, 1024, 8192,  8192, 65536
		

Crossrefs

T(n, n) = A046161(n).
Cf. A348679 (numerators), A347928, A088802 & A123854 (central elements).

Programs

  • Maple
    # Polynomials M are defined in A347928.
    T := (n, k) -> denom(coeff(M(n, x), x, k)):
    for n from 0 to 9 do seq(T(n, k), k = 0..n) od;

A364660 Numerators of coefficients in expansion of (1 + x)^(1/4).

Original entry on oeis.org

1, 1, -3, 7, -77, 231, -1463, 4807, -129789, 447051, -3129357, 11094993, -159028233, 574948227, -4188908511, 15359331207, -906200541213, 3358272593907, -25000473754641, 93422822977869, -1401342344668035, 5271716439465465, -39777496770512145, 150462705175415505, -4564035390320936985
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 01 2023

Keywords

Examples

			(1 + x)^(1/4) = 1 + x/4 - 3*x^2/32 + 7*x^3/128 - 77*x^4/2048 + 231*x^5/8192 - 1463*x^6/65536 + ...
Coefficients are 1, 1/4, -3/32, 7/128, -77/2048, 231/8192, -1463/65536, ...
		

Crossrefs

Denominators are A088802, A123854.

Programs

  • Mathematica
    nmax = 24; CoefficientList[Series[(1 + x)^(1/4), {x, 0, nmax}], x] // Numerator
    Table[Binomial[1/4, n], {n, 0, 24}] // Numerator
  • PARI
    my(x='x+O('x^30)); apply(numerator, Vec((1 + x)^(1/4))) \\ Michel Marcus, Aug 02 2023

A364661 Numerators of coefficients in expansion of (1 + x)^(3/4).

Original entry on oeis.org

1, 3, -3, 5, -45, 117, -663, 1989, -49725, 160225, -1057485, 3556995, -48612265, 168273225, -1177912575, 4161957765, -237231592605, 851242773465, -6147864475025, 22326455198775, -325966245902115, 1195209568307755, -8801088639357105, 32525762362841475, -964930950097630425
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 01 2023

Keywords

Examples

			(1 + x)^(3/4) = 1 + 3*x/4 - 3*x^2/32 + 5*x^3/128 - 45*x^4/2048 + 117*x^5/8192 - 663*x^6/65536 + ...
Coefficients are 1, 3/4, -3/32, 5/128, -45/2048, 117/8192, -663/65536, ...
		

Crossrefs

Denominators are A088802, A123854.

Programs

  • Mathematica
    nmax = 24; CoefficientList[Series[(1 + x)^(3/4), {x, 0, nmax}], x] // Numerator
    Table[Binomial[3/4, n], {n, 0, 24}] // Numerator
  • PARI
    my(x='x+O('x^30)); apply(numerator, Vec((1 + x)^(3/4))) \\ Michel Marcus, Aug 02 2023

A088801 Numerators of coefficients of powers of n^(-1) in the Romanovsky series expansion of the mean of the standard deviation from a normal population.

Original entry on oeis.org

1, -3, -7, -9, 59, 483, -2323, -42801, 923923, 30055311, -170042041, -8639161167, 99976667055, 7336972779615, -42962450319915, -4309733345367105, 203289825295660035, 26751125064470578695, -158415664732997134045, -26488943422458070446915
Offset: 0

Views

Author

Eric W. Weisstein, Oct 16 2003

Keywords

Comments

Asymptotic expansion of Gamma(N/2) / Gamma((N-1)/2) = (N/2)^(1/2) * (c(0) + c(1)/N + c(2)/N^2 + ... ). a(n) = numerator(c(n)). - Michael Somos, Aug 23 2007

Examples

			b(N) = 1 - 3/(4N) - 7/(32N^2) - 9/(128N^3) + ...
		

Crossrefs

Cf. A088802.

Programs

  • Mathematica
    a[ n_] := If[ n < 0, 0, Module[{A = 1}, Do[ A += x^k / (4 k) SeriesCoefficient[ (A /. x -> x / (1 + 2 x))^2 - (A/(1 - x))^2 / (1 + 2 x) + O[x]^(k + 2), k + 1], {k, n}]; Numerator@Coefficient[A, x, n]]]; (* Michael Somos, May 24 2015 *)
  • PARI
    {a(n) = my(A); if(n < 0, 0, A = 1 + O(x) ; for( k = 1, n, A = truncate(A) + x^2 * O(x^k); A += x^k/4/k * polcoeff( subst( A, x, x/(1+2*x))^2 - A^2/(1-x)^2/(1+2*x), k+1 ) ); numerator( polcoeff( A, n ) ) ) }; /* Michael Somos, Aug 23 2007 */

Extensions

a

A292754 Numerators of coefficients in an asymptotic expansion of the Wallis sequence in inverse powers of n.

Original entry on oeis.org

1, -1, 5, -11, 83, -143, 625, -1843, 24323, 61477, -14165, -8084893, 31181719, 1682401061, -3166220215, -251783137859, 3865962456803, 394670372519917, -765052915887545, -98394908192751193, 384080734825119709, 60838795345430052431, -119312155199695296505, -22845758944383820991909
Offset: 0

Views

Author

N. J. A. Sloane, Sep 25 2017

Keywords

References

  • Chao-Ping Chen, Richard B. Paris, On the asymptotic expansions of products related to the Wallis, Weierstrass, and Wilf formulas, Applied Mathematics and Computation 293 (2017) 30-39. See (3.12).

Crossrefs

Cf. A088802 or A123854 (denominators).

Programs

  • Mathematica
    nu[j_] := (-1)^(j+1) ((4 - 2^(1-j)) BernoulliB[j+1] - (j+1) 2^(-j))/(j*(j + 1)); mu[j_] := mu[j] = If[j == 0, 1, Sum[k nu[k] mu[j-k], {k, j}]/j]; Table[Numerator@mu@n, {n, 0, 23}] (* Giovanni Resta, May 29 2019 *)
    Numerator[CoefficientList[Series[16^n/(Pi*(2*n + 1) * Binomial[2*n, n]^2), {n, Infinity, 20}], 1/n]] (* Vaclav Kotesovec, Jun 02 2019 *)
  • PARI
    nu(j) = (-1)^(j+1)*((4-2^(1-j))*bernfrac(j+1) - (j+1)*2^(-j))/(j*(j+1));
    mu(j) = if (j==0, 1, sum(k=1, j, k*nu(k)*mu(j-k))/j);
    a(n) = numerator(mu(n)); \\ Michel Marcus, May 29 2019

Formula

See (3.8) and (3.11) in Chen link.

Extensions

More terms from Michel Marcus, May 29 2019
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