A025748 -id:A025748 - cp's OEIS frontend

A254282 Expansion of (1 - (1 - 27x)^(1/3)) / (9x).

1, 9, 135, 2430, 48114, 1010394, 22084326, 496897335, 11428638705, 267430145697, 6345388002447, 152289312058728, 3690087176807640, 90143558176300920, 2217531531137002632, 54883905395640815142, 1365640704844474400298, 34141017621111860007450

Offset: 0

Vaclav Kotesovec, Jan 27 2015

Harvey P. Dale, Table of n, a(n) for n = 0..700

Cf. A000108, A008544, A254286, A254287, A025748.

[Round(3^(3*n)*Gamma(n+2/3)/(Gamma(2/3)*Gamma(n+2))): n in [0..30]]; // G. C. Greubel, Aug 10 2022

CoefficientList[Series[(1-(1-27*x)^(1/3))/(9*x),{x,0,20}],x]
CoefficientList[Series[Hypergeometric1F1[2/3,2,27*x],{x,0,20}],x] * Range[0,20]! (* Vaclav Kotesovec, Jan 28 2015 *)
nxt[{n_,a_}]:={n+1,((27n+18)*a)/(n+2)}; NestList[nxt,{0,1},20][[All,2]] (* Harvey P. Dale, Jun 03 2019 *)

[3^(3*n)*rising_factorial(2/3,n)/factorial(n+1) for n in (0..30)] # G. C. Greubel, Aug 10 2022

G.f.: (1 - (1-27*x)^(1/3)) / (9*x).
a(n) ~ 3^(3*n) / (Gamma(2/3) * n^(4/3)).
Recurrence: (n+1)*a(n) = 9*(3*n-1)*a(n-1).
a(n) = 27^n * Gamma(n+2/3) / (Gamma(2/3) * Gamma(n+2)).
E.g.f.: hypergeom([2/3], [2], 27*x). - Vaclav Kotesovec, Jan 28 2015
From Peter Bala, Sep 01 2017: (Start)
a(n) = (-1)^n*binomial(1/3, n+1)*3^(3*n+1). Cf. A000108(n) = (-1)^n*binomial(1/2, n+1)*2^(2*n+1).
a(n) = 3^n*A025748(n+1). (End)

A225439 Expansion of 3x/((1-(1-9x)^(1/3))(1-9x)^(2/3)).

Original entry on oeis.org

1, 3, 21, 162, 1305, 10773, 90342, 765936, 6546177, 56293380, 486451251, 4220183916, 36731240910, 320571837810, 2804298945840, 24580601689752, 215832643307217, 1898042178972285, 16714070686567620, 147360883148636850, 1300623629653125855

Offset: 0

Vladimir Kruchinin, May 08 2013

nonn

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Cf. A025748, A097188, A122868.

A225439 := n -> `if`(n=0,1,(GAMMA(n+2/3)/GAMMA(2/3)+GAMMA(n+1/3)/(GAMMA(1/3)))* 3^(2*n-1)/GAMMA(n+1)): seq(A225439(i),i=0..20); # Peter Luschny, Jul 05 2013

Table[Sum[Binomial[k,n-k]*3^k*(-1)^(n-k)*Binomial[n+k-1,n-1], {k,0,n}], {n,0,20}] (* Vaclav Kotesovec, May 22 2013 *)

a(n):=if n=0 then 1 else sum(binomial(k,n-k)*3^(k)*(-1)^(n-k)*binomial(n+k-1,n-1),k,0,n);

my(x='x+O('x^66)); Vec(3*x/((1-(1-9*x)^(1/3))*(1-9*x)^(2/3))) \\ Joerg Arndt, May 08 2013

{a(n)=local(B=(1-(1-9*x+x^2*O(x^n))^(1/3))/(3*x));polcoeff(1+x*B'/B, n, x)} \\ Paul D. Hanna, May 08 2013

a(n) = Sum_{k = 0..n} C(k,n-k)*3^(k)*(-1)^(n-k)*C(n+k-1,n-1), n>0, a(0)=1.
G.f.: A(x) = 1 + x*B'(x)/B(x), where B(x) = (1-(1-9*x)^(1/3))/(3*x) is the g.f. of A097188.
n*(n-1)*a(n) = 18*(n-1)^2*a(n-1) - 9*(3*n-5)*(3*n-4)*a(n-2). - Vaclav Kotesovec, May 22 2013
a(n) ~ 3^(2*n-1)/(GAMMA(2/3)*n^(1/3)). - Vaclav Kotesovec, May 22 2013
a(n) = ((Gamma(n+2/3)/Gamma(2/3))+(Gamma(n+1/3)/Gamma(1/3)))*3^(2*n-1)/Gamma(n+1) for n > 0. - Peter Luschny, Jul 05 2013
From Peter Bala, Mar 11 2022: (Start)
a(n) = [x^n] (1/(1 - 3*x + 3*x^2))^n. Cf. A122868(n) = [x^n] (1 + 3*x + 3*x^2)^n.
The Gauss congruences a(n*p^k) == a(n*p^(k-1)) (mod p^k) hold for all primes p and positive integers n and k. (End)

A283151 Triangle read by rows: Riordan array (1/(1-9x)^(2/3), x/(9x-1)).

Original entry on oeis.org

1, 6, -1, 45, -15, 1, 360, -180, 24, -1, 2970, -1980, 396, -33, 1, 24948, -20790, 5544, -693, 42, -1, 212058, -212058, 70686, -11781, 1071, -51, 1, 1817640, -2120580, 848232, -176715, 21420, -1530, 60, -1, 15677145, -20902860, 9754668, -2438667, 369495, -35190, 2070, -69, 1, 135868590, -203802885

Offset: 0

Tom Richardson, Mar 01 2017

This is an example of a Riordan group involution.
Dual Riordan array of A283150.
With A283150 and A248324, forms doubly infinite Riordan array. For b and c the sequences A283150 and A248324, respectively, and i,j >= 0, the doubly infinite array with d(i,j) = a(i,j), d(-j,-i) = b(i,j), d(i,-j) = c(i,j), and d(-i,j) = 0 (except d(0,0)=1) is a doubly infinite Riordan array.

			Triangle begins
         1;
         6,        -1;
        45,       -15,       1;
       360,      -180,      24,       -1;
      2970,     -1980,     396,      -33,      1;
     24948,    -20790,    5544,     -693,     42,     -1;
    212058,   -212058,   70686,   -11781,   1071,    -51,    1;
   1817640,  -2120580,  848232,  -176715,  21420,  -1530,   60,  -1;
  15677145, -20902860, 9754668, -2438667, 369495, -35190, 2070, -69, 1;

Peter Bala, A 4-parameter family of embedded Riordan arrays
Peter Bala, A note on the diagonals of a proper Riordan Array
H. Prodinger, Some information about the binomial transform, The Fibonacci Quarterly, 32, 1994, 412-415.
Thomas M. Richardson, The three 'R's and Dual Riordan Arrays, arXiv:1609.01193 [math.CO], 2016.

Cf. A004988, A248324, A283150, A025748, A046521.

a(m,n) = binomial(-n-2/3, m-n)*(-1)^m*9^(m-n).
G.f.: (1-9x)^(1/3)/(xy-9x+1).
Recurrence: a(m,n) = a(m,n-1)*(n-1-m)/(9*n-3) for 0 < n <= m; matrix inverse of a(m,n) is a(m,n). - Werner Schulte, Aug 05 2017
From Peter Bala, Mar 05 2018 (Start):
Let P(n,x) = Sum_{k = 0..n} T(n,k)*x^(n-k) denote the n-th row polynomial in descending powers of x. Then (-1)^n*P(n,x) is the n-th degree Taylor polynomial of (1 - 9*x)^(n-1/3) about 0. For example, for n = 4 we have (1 - 9*x)^(11/3) = 2970*x^4 - 1980*x^3 + 396*x^2 - 33*x + 1 + O(x^5).
Let R(n,x) denote the n-th row polynomial of this triangle. The polynomial R(n,9*x) has the e.g.f. Sum_{k = 0..n} T(n,k)*(9*x)^k/k!. The e.g.f. for the n-th diagonal of the triangle (starting at n = 0 for the main diagonal) equals exp(-x) * the e.g.f. for the polynomial R(n,9*x). For example, when n = 3 we have exp(-x)*(360 - 180*(9*x) + 24*(9*x)^2/2! - (9*x)^3/3!) = 360 - 1980*x + 5544*x^2/2! - 11781*x^3/3! + 21420*x^4/4! - ....
Let F(x) = (1 - ( 1 - 9*x)^(1/3))/(3*x). See A025748. The derivatives of F(x) are related to the row polynomials P(n,x) by the identity x^n/n! * (d/dx)^n(F(x)) = 1/(3*x)*( (-1)^n - P(n,x)/(1 - 9*x)^(n-1/3) ), n = 0,1,2,.... Cf. A283151 and A046521. (End)
From Peter Bala, Aug 18 2021: (Start)
T(n,k) = (-1)^k*binomial(n-1/3, n-k)*9^(n-k).
Analogous to the binomial transform we have the following sequence transformation formula: g(n) = Sum_{k = 0..n} T(n,k)*b^(n-k)*f(k) iff f(n) = Sum_{k = 0..n} T(n,k)*b^(n-k)*g(k). See Prodinger, bottom of p. 413, with b replaced with 9*b, c = -1 and d = 2/3.
Equivalently, if F(x) = Sum_{n >= 0} f(n)*x^n and G(x) = Sum_{n >= 0} g(n)*x^n are a pair of formal power series then
G(x) = (1/(1 - 9*b*x)^(2/3)) * F(x/(1 - 9*b*x)) iff F(x) = (1/(1 + 9*b*x)^(2/3)) * G(x/(1 + 9*b*x)).
The infinitesimal generator of the unsigned array has the sequence (9*n+6) n>=0 on the main subdiagonal and zeros elsewhere. The m-th power of the unsigned array has entries m^(n-k)*|T(n,k)|. (End)

Offset corrected by Werner Schulte, Aug 05 2017

A218540 Reduced third-order Patalan numbers.

Original entry on oeis.org

1, 1, 1, 5, 10, 66, 154, 1122, 2805, 21505, 55913, 442221, 1179256, 9524760, 25852920, 211993944, 582983346, 4835332458, 13431479050, 112400272050, 314720761740, 2652646420380, 7475639911980, 63380425340700, 179577871798650, 1530003467724498

Offset: 0

R. J. Mathar, Nov 01 2012

Obtained by removing powers of 3 in a systematic manner from the Patalan numbers A025748.

Richard J. Mathar, Series expansion of generalized Fresnel integrals, arXiv:1211.3963 [math.CA], 2012, eq. (4.19).

Cf. A025748, A073006, A108411.

A218540 := proc(n)
    option remember;
    if n <=2 then
        1;
    elif n = 3 then
        5 ;
    else
        (n-1)*(n-2)*(n+4)*procname(n-1)-3*(3*n-4)*(3*n-7)*(n+2)*procname(n-2)-3*(3*n-10)*(n+4)*(3*n-7)*procname(n-3) ;
        -%/n/(n+2)/(n-1) ;
    end if;
end proc:

a[n_] := 3^(2*n-2-Floor[n/2]) * Pochhammer[2/3, n-1]/n!; a[0] = 1; Array[a, 26, 0] (* Amiram Eldar, Aug 20 2025 *)

a(n) = A025748(n)/A108411(n).
D-finite with recurrence n*(n+2)*(n-1)*a(n) + (n-1)*(n-2)*(n+4)*a(n-1) - 3*(3*n-4)*(3*n-7)*(n+2)*a(n-2) - 3*(3*n-10)*(n+4)*(3*n-7)*a(n-3) = 0, n >= 4.
a(n) ~ 3^(2*n-2-floor(n/2)) / (Gamma(2/3) * n^(4/3)). - Amiram Eldar, Aug 20 2025

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A254282 Expansion of (1 - (1 - 27*x)^(1/3)) / (9*x).

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A225439 Expansion of 3*x/((1-(1-9*x)^(1/3))*(1-9*x)^(2/3)).

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A283151 Triangle read by rows: Riordan array (1/(1-9x)^(2/3), x/(9x-1)).

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A218540 Reduced third-order Patalan numbers.

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A254282 Expansion of (1 - (1 - 27x)^(1/3)) / (9x).

A225439 Expansion of 3x/((1-(1-9x)^(1/3))(1-9x)^(2/3)).