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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A160657 a(n) is the period of a 2 X 4n rectangular oscillator in the 2 X 2 (B36/S125) Life-like cellular automaton.

Original entry on oeis.org

2, 6, 14, 14, 62, 126, 30, 30, 1022, 126, 4094, 2046, 1022, 32766, 62, 62, 8190, 174762, 8190, 2046, 254, 8190, 16777214, 4194302, 510, 134217726, 2097150, 1022, 1073741822, 2147483646, 126, 126, 17179869182, 8388606, 68719476734, 1022, 2097150, 2147483646
Offset: 1

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Author

Nathaniel Johnston, May 22 2009

Keywords

Comments

These oscillators work and have the same period in any rule from B3/S5 to B3678/S012567.
The Nathaniel Johnston rectangular oscillator link points to Sierpinski's gasket (Pascal's triangle mod 2) as a source for the chaotic terms of A003558. This is consistent with the comment of [Sep 21 2011, A003558] showing an alternative trigonometric connection to A054142, since the latter row terms are found as alternate ascending diagonals in Pascal's triangle. - Gary W. Adamson, Sep 21 2011
From Charlie Neder, Jan 11 2019: (Start)
a(n) = A268754(2n).
Proof: Decompose the phases of the oscillators into rectangles, as in the linked paper. Each of these rectangles has a corner on the exterior of the bounding diamond of the oscillator which determines the rectangle. As shown in the paper, these corners behave as Rule 90 on a width-n strip, which is exactly what A268754 emulates. Since the initial 2 X 4n block used in this sequence corresponds to the one-cell "seed" used in A268754, the resulting patterns must have the same period. (End)

Examples

			a(2) = 6 because a 2 X 8 box has period 6 in this rule.
		

Crossrefs

Programs

  • Mathematica
    g = Function[{sq, p}, Module[{l = Length[sq]},
    Do[If[sq[[i]] == sq[[j]], Return[p^(j - 1) - p^(i - 1)]],
    {j, 2, l}, {i, 1, j - 1}]]];
    MPM = Algebra`MatrixPowerMod;
    EventualPeriod = Function[{m, v, p},
    Module[{n = Length[m], w, sq, k, primes},
    sq = NestList[(MPM[#, p, p]) &, m, n];
    w = Mod[Last[sq].v, p];
    sq = Map[(Mod[#.w, p]) &, sq];
    k = g[sq, p];
    If[k == Null, k = p^n Apply[LCM, Table[p^r - 1, {r, 1, n}]]];
    primes = Map[First, FactorInteger[k]];
    primes = Select[primes, (# > 1) &];
    While[Length[primes] > 0,
    primes = Select[primes, (Mod[k, #] == 0) &];
    primes = Select[primes, (Mod[MPM[m, k/#, p].w, p] == w) &];
    k = k/Fold[Times, 1, primes];
    ]; k ]];
    mat = Function[{n}, Table[Boole[Abs[i - j] == 1], {i, 1, n}, {j, 1, n}]];
    vec = Function[{n}, Table[Boole[i == 1], {i, 1, n}]];
    Table[EventualPeriod[mat[2 n], vec[2 n], 2], {n, 1, 100}]
    (* Adam P. Goucher, Jan 13 2019 *)

Formula

a(n) divides 2^(A003558(n) + 1) - 2 for n >= 1. [Corrected by Charlie Neder, Jan 11 2019]

Extensions

a(18) corrected by Charlie Neder, Jan 11 2019

A375450 Expansion of g.f. A(x) satisfying 0 = Sum_{k=0..n} (-1)^k * binomial(2*n-k,k) * ([x^k] A(x)^n) for n >= 1.

Original entry on oeis.org

1, 1, 2, 9, 75, 960, 17056, 398023, 11785624, 431999096, 19225521917, 1022238356603, 64053139874787, 4673871388801269, 393051019651091208, 37747728969729478069, 4106730533743416782815, 502513668471090178354603, 68716238916399477889072499, 10440633447359638146139853297
Offset: 0

Views

Author

Paul D. Hanna, Sep 11 2024

Keywords

Comments

Note that 0 = Sum_{k=0..n} (-1)^k * binomial(n+k,2*k) * ([x^k] C(x)^n) for n >= 1 is satisfied by the Catalan function C(x) = 1 + x*C(x)^2 (A000108), where coefficient [x^k] C(x)^n = binomial(n+2*k-1,k)*n/(n+k).

Examples

			G.f.: A(x) = 1 + x + 2*x^2 + 9*x^3 + 75*x^4 + 960*x^5 + 17056*x^6 + 398023*x^7 + 11785624*x^8 + 431999096*x^9 + ...
RELATED TABLES.
The table of coefficients of x^k in A(x)^n begins:
  n=1: [1, 1,  2,   9,  75,  960,  17056, ...];
  n=2: [1, 2,  5,  22, 172, 2106,  36413, ...];
  n=3: [1, 3,  9,  40, 297, 3477,  58412, ...];
  n=4: [1, 4, 14,  64, 457, 5120,  83454, ...];
  n=5: [1, 5, 20,  95, 660, 7091, 112010, ...];
  n=6: [1, 6, 27, 134, 915, 9456, 144632, ...];
  ...
from which we may illustrate the defining property given by
0 = Sum_{k=0..n} (-1)^k * binomial(2*n-k,k) * ([x^k] A(x)^n).
Using the coefficients in the table above, we see that
  n=1: 0 = 1*1 - 1*1;
  n=2: 0 = 1*1 - 3*2 + 1*5;
  n=3: 0 = 1*1 - 5*3 + 6*9 - 1*40;
  n=4: 0 = 1*1 - 7*4 + 15*14 - 10*64 + 1*457;
  n=5: 0 = 1*1 - 9*5 + 28*20 - 35*95 + 15*660 - 1*7091;
  n=6: 0 = 1*1 - 11*6 + 45*27 - 84*134 + 70*915 - 21*9456 + 1*144632;
  ...
The triangle A054142(n,k) = binomial(2*n-k,k) begins:
  n=0: 1;
  n=1: 1,  1;
  n=2: 1,  3,  1;
  n=3: 1,  5,  6,  1;
  n=4: 1,  7, 15, 10,  1;
  n=5: 1,  9, 28, 35, 15,  1;
  n=6: 1, 11, 45, 84, 70, 21, 1;
  ...
		

Crossrefs

Programs

  • PARI
    {a(n) = my(A=[1]); for(i=1, n, A=concat(A, 0);
    A[#A] = sum(k=0, #A-1, (-1)^(#A-k) * binomial(2*(#A-1)-k, 1*k) * polcoef(Ser(A)^(#A-1), k) )/(#A-1) ); A[n+1]}
    for(n=0, 20, print1(a(n), ", "))

Formula

a(n) ~ c * 2^(2*n) * n^(2*n + 3/2) / (exp(2*n) * Pi^(2*n)), where c = 35.20725926431251936515... - Vaclav Kotesovec, Sep 11 2024

A027989 a(n) = self-convolution of row n of array T given by A027926.

Original entry on oeis.org

1, 3, 10, 33, 105, 324, 977, 2895, 8462, 24465, 70101, 199368, 563425, 1583643, 4430290, 12342849, 34262337, 94800780, 261545777, 719697255, 1975722326, 5412138033, 14796520365, 40380240528, 110016825025, 299285288499, 813011578522, 2205652007265, 5976479585817
Offset: 0

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Author

Keywords

Comments

a(n) is the number of all columns in stack polyominoes of perimeter 2n+4. - Emanuele Munarini, Apr 07 2011

Crossrefs

Programs

  • Mathematica
    Table[((5+4n)Fibonacci[1+2n]-(1+2n)Fibonacci[2n])/5,{n,0,28}] (* Emanuele Munarini, Apr 07 2011 *)
  • Maxima
    makelist(((5+4*n)*fib(1+2*n)-(1+2*n)*fib(2*n))/5,n,0,20); /* Emanuele Munarini, Apr 07 2011 */
    
  • PARI
    Vec((1-3*x+3*x^2)/(1-3*x+x^2)^2+O(x^66)) /* Joerg Arndt, Apr 08 2011 */

Formula

a(n) = (2/5)*(n + 1)*F(2*n+3) + (1/5)*F(2*n+2) - (4/5)*(n + 1)*F(2*n), where F(n) = A000045(n). - Ralf Stephan, May 13 2004
From Emanuele Munarini, Apr 07 2011: (Start)
a(n) = ((4*n + 5)*F(2*n+1) - (2*n + 1)*F(2*n))/5, where F(n) = A000045(n).
a(n) = Sum_{k=0..n} binomial(2*n-k, k)*(k + 1).
G.f.: (1 - 3*x + 3*x^2)/(1 - 3*x + x^2)^2.
a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3) - a(n-4). (End)

A098435 Triangle of Salie numbers T(n,k) for negative n,k, n < k.

Original entry on oeis.org

1, -1, 1, 2, -3, 1, -8, 13, -6, 1, 56, -92, 45, -10, 1, -608, 1000, -493, 115, -15, 1, 9440, -15528, 7662, -1799, 245, -21, 1, -198272, 326144, -160944, 37817, -5180, 462, -28, 1, 5410688, -8900224, 4392080, -1032088, 141465, -12684, 798, -36, 1
Offset: 1

Views

Author

Ralf Stephan, Sep 08 2004

Keywords

Comments

Inverse matrix of A054142. - Paul Barry, Jan 21 2005
Essentially the same as the triangle giving by [0,-1,-1,-4,-4,-9,-9,-16,-16,-25,...] DELTA[1,0,1,0,1,0,1,0,1,0,...] = 1; 0,1; 0,-1,1; 0,2,-3,1; 0,-8,13,-6,1; 0,56,-92,45,-10,1; ... where DELTA is the operator defined in A084938. - Philippe Deléham, Aug 30 2006

Examples

			   1;
  -1,   1;
   2,  -3,   1;
  -8,  13,  -6,   1;
  56, -92,  45, -10,  1;
		

Crossrefs

T(-1, k) = (-1)^k*A005439(k-1). Row sums are zero.

Programs

  • Mathematica
    rows = 9; A054142 = Table[ PadRight[ Table[ Binomial[2*n-k, k], {k, 0, n}], rows], {n, 0, rows-1}]; inv = Inverse[A054142]; Table[ Take[inv[[n]], n], {n, 1, rows}] // Flatten (* Jean-François Alcover, Oct 02 2013, after Paul Barry *)

Formula

See A065547 for formulas.

A109223 Number triangle related to the Fibonacci polynomials.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 3, 5, 1, 1, 1, 6, 5, 7, 1, 1, 1, 6, 15, 7, 9, 1, 1, 1, 10, 15, 28, 9, 11, 1, 1, 1, 10, 35, 28, 45, 11, 13, 1, 1, 1, 15, 35, 84, 45, 66, 13, 15, 1, 1, 1, 15, 70, 84, 165, 66, 91, 15, 17, 1, 1, 1, 21, 70, 210, 165, 286, 91, 120, 17, 19, 1, 1, 1, 21, 126, 210
Offset: 0

Views

Author

Paul Barry, Jun 22 2005

Keywords

Comments

Riordan array (1/(1-x), x/(1-x^2)^2). Row-reversal of number triangle A109221. Diagonals form a repeated version of A054142. Row sums are A109222. Diagonal sums are A094967.

Examples

			Rows begin
  1;
  1,  1;
  1,  1,  1;
  1,  3,  1,  1;
  1,  3,  5,  1,  1;
  1,  6,  5,  7,  1,  1;
  1,  6, 15,  7,  9,  1,  1;
		

Programs

Formula

T(n,k) = binomial(floor((n+k)/2)+k, 2*k)
T(n,k) = A065941(n+k,n-k). - Johannes W. Meijer, Aug 14 2011

A172991 Triangle of binomial sums read by rows: T(n,k) = sum(C(2n-2k-i,i) * C(2k-i,i), i=0..min(k,n-k)).

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 4, 4, 1, 1, 6, 11, 6, 1, 1, 8, 22, 22, 8, 1, 1, 10, 37, 63, 37, 10, 1, 1, 12, 56, 136, 136, 56, 12, 1, 1, 14, 79, 249, 376, 249, 79, 14, 1, 1, 16, 106, 410, 849, 849, 410, 106, 16, 1, 1, 18, 137, 627, 1663, 2317, 1663, 627, 137, 18, 1, 1, 20, 172, 908, 2942, 5371, 5371, 2942, 908, 172, 20, 1, 1, 22, 211, 1261, 4826, 11017, 14545, 11017, 4826, 1261, 211, 22, 1
Offset: 0

Views

Author

Emanuele Munarini, Apr 07 2011

Keywords

Comments

The matrix inverse starts
1;
-1,1;
1,-2,1;
-1,4,-4,1;
0,-8,13,-6,1;
7,12,-38,26,-8,1;
-35,-12,114,-101,43,-10,1; - R. J. Mathar, Mar 22 2013

Examples

			G.f. =
1 +
(y + 1)*x +
(y^2 + 2*y + 1)*x^2 +
(y^3 + 4*y^2 + 4*y + 1)*x^3 +
(y^4 + 6*y^3 + 11*y^2 + 6*y + 1)*x^4 + ...
Triangle begins:
1,
1,  1,
1,  2,  1,
1,  4,  4,   1,
1,  6, 11,   6,   1,
1,  8, 22,  22,   8,   1,
1, 10, 37,  63,  37,  10,  1,
1, 12, 56, 136, 136,  56, 12,  1,
1, 14, 79, 249, 376, 249, 79, 14,  1
		

Crossrefs

Programs

  • Mathematica
    Flatten[Table[Sum[Binomial[2n-2k-i,i]Binomial[2k-i,i],{i,0,Min[k,n-k]}],{n,0,12},{k,0,n}]]
  • Maxima
    create_list(sum(binomial(2*n-2*k-i,i)*binomial(2*k-i,i),i,0,min(k,n-k)),n,0,10,k,0,n);

Formula

G.f.: (1 -x -x*y -2*x^2*y +x^3*y +x^3*y^2 +4*x^4*y^2 -x^6*y^3) / (1 -2*x +x^2 -2*x*y+2*x^3*y +x^2*y^2 +2*x^3*y^2 +3*x^4*y^2 -2*x^5*y^2 -2*x^5*y^3 -6*x^6*y^3 +x^8*y^4).
Central coefficients T(2n,n) = A188648.

A192398 a(n) = n^4 + 3*n^3 - 3*n.

Original entry on oeis.org

1, 34, 153, 436, 985, 1926, 3409, 5608, 8721, 12970, 18601, 25884, 35113, 46606, 60705, 77776, 98209, 122418, 150841, 183940, 222201, 266134, 316273, 373176, 437425, 509626, 590409, 680428, 780361, 890910, 1012801, 1146784, 1293633, 1454146, 1629145, 1819476
Offset: 1

Views

Author

Gary W. Adamson, Jun 30 2011

Keywords

Comments

Related to the 9-gon (nonagon). Following Steinbach's strategy re: "Diagonal Product Formulas" and applied to the 9-gon (nonagon), we extract the constants (a, b, c, d) as e-vals of the 4 X 4 tridiagaonal matrix with (1's in the super and subdiagonals), (1,2,2,2), and the rest zeros. The charpoly of this matrix is row 4 of A054142, a Morgan-Voyce polynomial: x^4 - 7*x^3 + 15*x^2 + 10*x - 1 = 0. Following Steinbach's procedure, let the matrix = M; then find the first four rows of M^n * [1,0,0,0,...] getting (1; 1,1; 2,3,1; 5,9,5,1). Using the SIMULT operation, we equate each of these rows to successive powers of the constant c (largest e-val of matrix M), 3.5320888...as follows: SIMULT: [1,0,0,0] = 1; [1,1,0,0] = c; [2,3,1,0] = c^2; [5,9,5,1] = c^3. Solving, we obtain the four distinct diagonals of the 9-gon (nonagon) with edge = 1: (1, 2.5320888,..., 2.879385,..., and 1.879385,...).
The sequence is column 3 in the array of A162997.
Analogous sequences using the matrix M^k generator -M^2 generates A028387: (1, 5, 11, 19, 29, 41,...); M^3 generates A123972: (1, 13, 41, 91, 169,...).

Examples

			a(5) = 5^4 + 3*5^3 - 3*5 = (625 + 375 - 15) = 985.
a(4) = 436 = (1, 3, 3, 1) dot (1, 33, 86, 78) = (1 + 99 + 258 + 78) = 436.
a(7) = 3409 = lower right term in M^4, M = {{1,6}{1,7}}.
a(4) = 436 = (3 + a) * (3 + b) * (3 + c) * (3 + d), = (5.347296...) * (3.120614...) * (4) * (6.532088...) = 436.
		

Crossrefs

Programs

Formula

G.f.: (1 +29*x -7*x^2 +x^3) / (1-x)^5. - R. J. Mathar, Jul 08 2011
a(n) = binomial transform of [1, 33, 86, 78, 24, 0, 0, 0,...].
a(n) = lower right term in the 2 X 2 matrix M^4, M = {{1,n-1}, {1,n}}.
a(n) = ((n-1) + a) * ((n-1) + b) * ((n-1) + c) * ((n-1) + d), where a, b, c, d, = {k=1,2,3,4} 4*cos^2 (2*Pi*k)/9.
E.g.f.: x*(1 + 16*x + 9*x^2 + x^3)*exp(x). - G. C. Greubel, Jul 11 2023

A121529 Triangle read by rows: T(n,k) is the number of nondecreasing Dyck paths of semilength n and having k double rises at an odd level (n >= 1, k >= 0).

Original entry on oeis.org

1, 1, 1, 1, 4, 1, 10, 2, 1, 19, 14, 1, 33, 50, 5, 1, 55, 132, 45, 1, 90, 301, 205, 13, 1, 146, 631, 680, 139, 1, 236, 1255, 1892, 763, 34, 1, 381, 2409, 4717, 3019, 419, 1, 615, 4509, 10920, 9846, 2677, 89, 1, 993, 8283, 23974, 28292, 12241, 1241, 1, 1604, 14998
Offset: 1

Views

Author

Emeric Deutsch, Aug 05 2006

Keywords

Comments

A nondecreasing Dyck path is a Dyck path for which the sequence of the altitudes of the valleys is nondecreasing.
Row n contains 1+floor(n/2) terms.
Row sums are the odd-indexed Fibonacci numbers (A001519).
T(2n,n) = Fibonacci(2n-1) (A001519).
Sum_{k>=0} k*T(n,k) = A121530(n).

Examples

			T(4,2)=2 because we have U/UDDU/UDD and U/UU/UDDDD, where U=(1,1) and D=(1,-1) (the double rises at an odd level are indicated by a /).
Triangle starts:
  1;
  1,  1;
  1,  4;
  1, 10,  2;
  1, 19, 14;
  1, 33, 50,  5;
		

Crossrefs

Programs

  • Maple
    G:=z*(1-t*z^2)*(1-z+t*z-z^2-t*z^2-t^2*z^3)/(1-z-t*z^2)/(1-z-z^2-3*t*z^2-t*z^3+t^2*z^4): Gser:=simplify(series(G,z=0,18)): for n from 1 to 15 do P[n]:=sort(coeff(Gser,z,n)) od: for n from 1 to 15 do seq(coeff(P[n],t,j),j=0..floor(n/2)) od; # yields sequence in triangular form

Formula

G.f.: G(t,z) = z*(1-tz^2)*(1 - z + tz - z^2 - tz^2 - t^2*z^3)/((1 - z - tz^2)*(1 - z - z^2 - 3tz^2 - tz^3 + t^2*z^4)).

A144252 Eigentriangle, row sums = A144251 shifted, right border = A144251.

Original entry on oeis.org

1, 1, 1, 1, 3, 2, 1, 5, 12, 6, 1, 7, 30, 60, 24, 1, 9, 56, 210, 360, 122, 1, 11, 90, 504, 1680, 2562, 758, 1, 13, 132, 990, 5040, 15372, 21224, 5606, 1, 15, 182, 1716, 11880, 36364, 159180, 201816, 47378, 1, 17, 240, 2730, 24024, 157014, 700392, 1849980, 2177010, 479532
Offset: 0

Views

Author

Gary W. Adamson, Sep 16 2008

Keywords

Comments

Right border = A144251: (1, 1, 2, 6, 24, 122, 758,...) with row sums = the same sequence shifted. Sum of n-th row terms = rightmost term of next row.

Examples

			First few rows of the triangle =
  1;
  1, 1;
  1, 3, 2;
  1, 5, 12, 6;
  1, 7, 30, 60, 24;
  1, 9, 56, 210, 360, 122;
  1, 11, 90, 504, 1680, 2562, 758;
  1, 13, 132, 990, 5040, 15372, 21224, 5606;
  ...
The triangle is generated from A054142 and its own eigensequence, A144251.
Triangle A054142 =
  1;
  1, 1;
  1, 3, 1;
  1, 5, 6, 1;
  1, 7, 15, 10, 1;
  ...
The eigensequence of A054142 = A144251: (1, 1, 2, 6, 24, 122, 758, 5606,...);
Example: row 3 of A144252 = (1, 5, 12, 6) = termwise products of (1, 5, 6, 1) and (1, 1, 2, 6) = (1*1, 5*1, 6*2, 1*6).
		

Crossrefs

Programs

  • PARI
    A054142(n, k) = binomial(2*n-k, k);
    V144251(nn) = my(v=vector(nn)); v[1] = 1; for (n=2, nn, v[n] = sum(k=0, n-1, A054142(n-2,k)*v[k+1]);); v;
    row(n) = my(v=V144251(n+1)); vector(n+1, k, A054142(n,k-1) * v[k]); \\ Michel Marcus, Jan 18 2025

Formula

Eigentriangle by rows, T(n,k) = A054142(n,k) * A144251(k); were A144251 = the eigensequence of triangle A054142.

Extensions

More terms from Michel Marcus, Jan 18 2025

A171822 Triangle T(n,k) = binomial(2*n-k, k)*binomial(n+k, 2*k), read by rows.

Original entry on oeis.org

1, 1, 1, 1, 9, 1, 1, 30, 30, 1, 1, 70, 225, 70, 1, 1, 135, 980, 980, 135, 1, 1, 231, 3150, 7056, 3150, 231, 1, 1, 364, 8316, 34650, 34650, 8316, 364, 1, 1, 540, 19110, 132132, 245025, 132132, 19110, 540, 1, 1, 765, 39600, 420420, 1288287, 1288287, 420420, 39600, 765, 1
Offset: 0

Views

Author

Roger L. Bagula, Dec 19 2009

Keywords

Examples

			Triangle begins as:
  1;
  1,    1;
  1,    9,     1;
  1,   30,    30,       1;
  1,   70,   225,      70,       1;
  1,  135,   980,     980,     135,       1;
  1,  231,  3150,    7056,    3150,     231,       1;
  1,  364,  8316,   34650,   34650,    8316,     364,       1;
  1,  540, 19110,  132132,  245025,  132132,   19110,     540,     1;
  1,  765, 39600,  420420, 1288287, 1288287,  420420,   39600,   765,    1;
  1, 1045, 75735, 1166880, 5465460, 9018009, 5465460, 1166880, 75735, 1045, 1;
		

Crossrefs

Programs

  • Magma
    [Binomial(2*n-k, k)*Binomial(n+k, 2*k): k in [0..n], n in [0..10]]; // G. C. Greubel, Feb 22 2021
  • Mathematica
    Table[Binomial[2*n-k, k]*Binomial[n+k, 2*k], {n,0,10}, {k,0,n}]//Flatten
  • Sage
    flatten([[binomial(2*n-k, k)*binomial(n+k, 2*k) for k in (0..n)] for n in (0..10)]) # G. C. Greubel, Feb 22 2021
    

Formula

T(n, k) = binomial(2*n-k, k)*binomial(n+k, 2*k) = A054142(n, k)*A085478(n, k).
Sum_{k=0..n} T(n, k) = Hypergeometric 4F3([-n, -n, 1/2 -n, n+1], [1/2, 1, -2*n], 1) = A183160(n). - G. C. Greubel, Feb 22 2021

Extensions

Edited by G. C. Greubel, Feb 22 2021
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