A058387
Number of series-parallel networks with n unlabeled edges, multiple edges not allowed.
Original entry on oeis.org
0, 1, 1, 2, 4, 8, 18, 40, 94, 224, 548, 1356, 3418, 8692, 22352, 57932, 151312, 397628, 1050992, 2791516, 7447972, 19950628, 53635310, 144664640, 391358274, 1061628772, 2887113478, 7869761108, 21497678430, 58841838912, 161356288874
Offset: 0
From _Andrew Howroyd_, Dec 22 2020: (Start)
In the following examples, elements in series are juxtaposed and elements in parallel are separated by '|'. The unit element (an edge) is denoted by 'o'.
a(1) = 1: (o).
a(2) = 1: (oo).
a(3) = 2: (ooo), (o|oo).
a(4) = 4: (oooo), (o(o|oo)), (o|ooo), (oo|oo).
a(5) = 8: (ooooo), (oo(o|oo)), (o(o|ooo)), (o(oo|oo)), (o|oooo), (o|o(o|oo)), (oo|ooo), (o|oo|oo).
(End)
- Andrew Howroyd, Table of n, a(n) for n = 0..500
- Steven R. Finch, Series-parallel networks
- Steven R. Finch, Series-parallel networks, July 7, 2003. [Cached copy, with permission of the author]
- John W. Moon, Some enumerative results on series-parallel networks, Annals Discrete Math., 33 (1987), 199-226 (the sequence v_n).
- Index entries for sequences mentioned in Moon (1987)
A000084 is the case that multiple edges are allowed.
A058381 is the case that edges are labeled.
A339290 is the case that order is significant in series configurations.
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EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
seq(n)={my(s=p=vector(n)); p[1]=1; for(n=2, n, s[n]=EulerT(p[1..n])[n]; p[n]=vecsum(EulerT(s[1..n])[n-1..n])-s[n]); concat([0], p+s)} \\ Andrew Howroyd, Dec 22 2020
A234289
E.g.f. satisfies: A(x) = 1 + A(x)^2 * Integral 1/A(x) dx.
Original entry on oeis.org
1, 1, 3, 17, 147, 1729, 25827, 468593, 10012083, 246287521, 6856204803, 213102768977, 7315460977107, 274894137157249, 11223280473993507, 494715928976218673, 23416019742035332083, 1184519963466363339361, 63774753426394808946243, 3641219528568659379843857
Offset: 0
E.g.f.: A(x) = 1 + x + 3*x^2/2! + 17*x^3/3! + 147*x^4/4! + 1729*x^5/5! +...
where A(x)^2 = 1 + 2*x + 8*x^2/2! + 52*x^3/3! + 484*x^4/4! + 5948*x^5/5! +...
Integral 1/A(x) dx = x - x^2/2! - x^3/3! - 5*x^4/4! - 41*x^5/5! - 469*x^6/6! +...
Further,
Series_Reversion(Integral 1/A(x) dx) = x + x^2/2 + 2*x^3/3 + 5*x^4/4 + 14*x^5/5 + 42*x^6/6 + 132*x^7/7 +...+ A000108(n-1)*x^n/n +...
where A000108(n) = binomial(2*n,n)/(n+1).
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seq(n! * coeff(series(-2/LambertW(-1,-2*exp(x-2)), x, n+1), x, n), n = 0..10) # Vaclav Kotesovec, Dec 27 2013
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CoefficientList[1 + InverseSeries[Series[2*x/(1+x) - Log[1+x], {x, 0, 20}], x],x]* Range[0, 20]! (* Vaclav Kotesovec, Dec 27 2013 *)
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{a(n)=local(A=1+x);for(i=1,n,A=1+A^2*intformal(1/(A+x*O(x^n))));n!*polcoeff(A,n)}
for(n=0,25,print1(a(n),", "))
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/* Explicit formula using Catalan function C(x) = 1 + x*C(x)^2: */
{a(n)=local(C=(1-sqrt(1-4*x+x^2*O(x^n)))/(2*x),A=1); A=1/deriv(serreverse(intformal(C))); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
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/* Explicit formula: 1 + Series_Reversion(2*x/(1+x) - log(1+x)): */
{a(n)=local(A=1,X=x+x^2*O(x^n)); A=1+serreverse(2*X/(1+X)-log(1+X)); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
A058478
Total number of interior nodes in all essentially series series-parallel networks with n labeled edges, multiple edges allowed.
Original entry on oeis.org
0, 0, 1, 5, 46, 534, 7596, 127756, 2479856, 54560512, 1341716960, 36468949824, 1085680795200, 35131589529152, 1227777836217856, 46086892351150592, 1849266301464495616, 78990342571085637120, 3578513340735623076864
Offset: 0
- J. W. Moon, Some enumerative results on series-parallel networks, Annals Discrete Math., 33 (1987), 199-226 (the e.g.f. I_S(x)).
A058479
Total number of interior nodes in all essentially parallel series-parallel networks with n labeled edges, multiple edges allowed.
Original entry on oeis.org
0, 0, 0, 3, 32, 410, 6164, 107492, 2140368, 47990784, 1197523456, 32930028736, 989647215424, 32276598717376, 1135501305508608, 42865272243657216, 1728443263014370304, 74145986811618564608, 3371731055491925101568
Offset: 0
- J. W. Moon, Some enumerative results on series-parallel networks, Annals Discrete Math., 33 (1987), 199-226 (the e.g.f. I_P(x)).
A234294
E.g.f. satisfies: A(x) = 1 + A(x)^4 * Integral 1/A(x)^4 dx.
Original entry on oeis.org
1, 1, 4, 40, 664, 15424, 460576, 16808320, 724904896, 36072438016, 2034328297984, 128223244372480, 8932539799788544, 681536817951791104, 56521548341146402816, 5062454448656689500160, 487013865350356256137216, 50082306316236214342844416, 5482502331779770770018893824
Offset: 0
E.g.f.: A(x) = 1 + x + 4*x^2/2! + 40*x^3/3! + 664*x^4/4! + 15424*x^5/5! +...
where A(4*log(1+x) - 3*x) = 1+x.
Related series:
A(x)^4 = 1 + 4*x + 28*x^2/2! + 328*x^3/3! + 5752*x^4/4! + 137056*x^5/5! +...
1/A(x)^4 = 1 - 4*x + 4*x^2/2! - 40*x^3/3! - 536*x^4/4! - 13216*x^5/5! +...
(d/dx Series_Reversion(Integral 1/A(x)^4 dx))^(1/4) begins:
G(x) = 1 + x + 4*x^2 + 22*x^3 + 140*x^4 + 969*x^5 +...+ A002293(n)*x^n +...
where G(x) = 1 + x*G(x)^4.
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CoefficientList[1 + InverseSeries[Series[4*Log[1+x]-3*x, {x, 0, 20}], x],x]* Range[0, 20]! (* Vaclav Kotesovec, Dec 26 2013 *)
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{a(n)=local(A=1+x); for(i=1, n, A=1+A^4*intformal(1/(A^4+x*O(x^n)))); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
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{a(n)=local(A=1, X=x+x^2*O(x^n)); A=1+serreverse(4*log(1+X) - 3*X); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
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/* O.g.f. continued fraction: */
{a(n)=local(CF=1+x*O(x)); for(k=0, n, CF=1-(n-k+1)*x-3*(n-k+1)*x/CF); polcoeff(1+x/CF, n, x)}
for(n=0, 25, print1(a(n), ", "))
A058561
A 3-way generalization of series-parallel networks with n labeled edges.
Original entry on oeis.org
0, 1, 3, 12, 78, 708, 8256, 117624, 1980096, 38456736, 846413472, 20819693568, 565998548352, 16852047061632, 545372109629184, 19061178127458816, 715541912895773184, 28713061759257037824, 1226513716981332031488
Offset: 0
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spec := [ N, {N=Union(Z,S,P,Q), S=Set(Union(Z,P),card>=2), P=Set(Union(Z,Q),card>=2), Q=Set(Union(Z,S),card>=2)}, labeled ]; [seq(combstruct[count](spec,size=n), n=0..40)]; # N = A058561, S=A000311
A190015
Triangle T(n,k) for solving differential equation A'(x)=G(A(x)), G(0)!=0.
Original entry on oeis.org
1, 1, 2, 1, 6, 8, 1, 24, 42, 16, 22, 1, 120, 264, 180, 192, 136, 52, 1, 720, 1920, 1248, 540, 1824, 2304, 272, 732, 720, 114, 1, 5040, 15840, 10080, 8064, 18720, 22752, 9612, 7056, 10224, 17928, 3968, 2538, 3072, 240, 1, 40320, 146160, 92160, 70560, 32256, 207360, 249120, 193536, 73728, 61560, 144720, 246816, 101844, 142704, 7936, 51048, 110448, 34304, 8334, 11616, 494, 1
Offset: 0
Triangle begins:
1;
1;
2,1;
6,8,1;
24,42,16,22,1;
120,264,180,192,136,52,1;
720,1920,1248,540,1824,2304,272,732,720,114,1;
5040,15840,10080,8064,18720,22752,9612,7056,10224,17928,3968,2538,3072,240,1;
40320,146160,92160,70560,32256,207360,249120,193536,73728,61560,144720,246816, 101844,142704,7936,51048,110448,34304,8334,11616,494,1;
Example for n=5:
partitions of number 9 into 5 parts in lexicographic order:
[1,1,1,1,5]
[1,1,1,2,4]
[1,1,1,3,3]
[1,1,2,2,3]
[1,2,2,2,2]
a(5) = (24*g(0)^4*g(4) +42*g(0)^3*g(1)*g(3) +16*g(0)^3*g(2)^2 +22*g(0)^2*g(1)^2*g(2) +g(0)*g(1)^4)/5!.
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/* array of triangle */
M:[1,1,2,1,6,8,1,24,42,16,22,1,120,264,180,192,136,52,1,720,1920,1248,540,1824,2304,272,732,720,114,1,5040,15840,10080,8064,18720,22752,9612,7056,10224,17928,3968,2538,3072,240,1,40320,146160,92160,70560,32256,207360,249120,193536,73728,61560,144720,246816,101844,142704,7936,51048,110448,34304,8334,11616,494,1];
/* function of triangle */
T(n,k):=M[sum(num_partitions(i),i,0,n-1)+k+1];
/* count number of partitions of n into m parts */
b(n,m):=if n
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/* Find triangle */
Co(n,k):=if k=1 then a(n) else sum(a(i+1)*Co(n-i-1,k-1),i,0,n-k);
a(n):=if n=1 then 1 else 1/n*sum(Co(n-1,k)*x(k),k,1,n-1);
makelist(ratsimp(n!*a(n)),n,1,5);
/* Vladimir Kruchinin, Jun 15 2012 */
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serlaplace( serreverse( intformal( 1 / sum(n=0, 9, eval(Str("g"n)) * x^n, x * O(x^9))))) /* Michael Somos, Oct 22 2014 */
A234295
E.g.f. satisfies: A(x) = 1 + A(x)^5 * Integral 1/A(x)^5 dx.
Original entry on oeis.org
1, 1, 5, 65, 1405, 42505, 1653125, 78578225, 4414067725, 286099718425, 21015972365525, 1725374840578625, 156560122048892125, 15559151967183795625, 1680744724811088153125, 196083244062052339084625, 24570430118524659881918125, 3291153805391398126661325625
Offset: 0
E.g.f.: A(x) = 1 + x + 5*x^2/2! + 65*x^3/3! + 1405*x^4/4! + 42505*x^5/5! +...
where A(5*log(1+x) - 4*x) = 1+x.
Related series:
A(x)^5 = 1 + 5*x + 45*x^2/2! + 685*x^3/3! + 15645*x^4/4! + 485645*x^5/5! +...
1/A(x)^5 = 1 - 5*x + 5*x^2/2! - 85*x^3/3! - 1595*x^4/4! - 50645*x^5/5! +...
(d/dx Series_Reversion(Integral 1/A(x)^5 dx))^(1/5) begins:
G(x) = 1 + x + 5*x^2 + 35*x^3 + 285*x^4 + 2530*x^5 +...+ A002294(n)*x^n +...
where G(x) = 1 + x*G(x)^5.
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CoefficientList[1 + InverseSeries[Series[5*Log[1+x]-4*x, {x, 0, 20}], x],x]* Range[0, 20]! (* Vaclav Kotesovec, Dec 26 2013 *)
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{a(n)=local(A=1+x); for(i=1, n, A=1+A^5*intformal(1/(A^5+x*O(x^n)))); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
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{a(n)=local(A=1,X=x+x^2*O(x^n)); A=1+serreverse(5*log(1+X) - 4*X); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
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/* O.g.f. continued fraction: */
{a(n)=local(CF=1+x*O(x)); for(k=0, n, CF=1-(n-k+1)*x-4*(n-k+1)*x/CF); polcoeff(1+x/CF, n, x)}
for(n=0, 25, print1(a(n), ", "))
A278458
Triangle T(n,k) read by rows: coefficients of polynomials P_n(t) defined in Formula section.
Original entry on oeis.org
1, 2, 2, 9, 15, 8, 64, 156, 144, 52, 625, 2050, 2675, 1730, 472, 7776, 32430, 55000, 50310, 25108, 5504, 117649, 599319, 1258775, 1484245, 1052184, 428036, 78416, 2097152, 12669496, 31902416, 46103680, 42064736, 24421096, 8389552, 1320064, 43046721, 301574340, 888996066, 1524644856, 1698413409, 1269814980, 625219644, 185935104, 25637824
Offset: 1
A(x;t) = x + (2*t+2)*x^2/2! + (9*t^2+15*t+8)*x^3/3! + (64*t^3+156*t^2+144*t+52)*x^4/4! + ...
Triangle starts:
n\k [1] [2] [3] [4] [5] [6] [7]
[1] 1;
[2] 2, 2;
[3] 9, 15, 8;
[4] 64, 156, 144, 52;
[5] 625, 2050, 2675, 1730, 472;
[6] 7776, 32430, 55000, 50310, 25108, 5504;
[7] 117649, 599319, 1258775, 1484245, 1052184, 428036, 78416;
[8] ...
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m = 10;
(Reverse[CoefficientList[#, t]]& /@ CoefficientList[InverseSeries[Log[x + Exp[t Log[1+x]]] - (t-1) Log[1+x] - x + O[x]^m], x]) Range[0, m-1]! // Rest // Flatten (* Jean-François Alcover, Sep 28 2019 *)
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N=10; x = 'x + O('x^N); t='t;
concat(apply(p->Vec(p), Vec(serlaplace(serreverse(log(x + exp(t*log(1+x))) - (t-1)*log(1+x) - x)))))
A302285
Expansion of 1/(1 - x - x/(1 - 2*x - x/(1 - 3*x - x/(1 - 4*x - x/(1 - 5*x - x/(1 - ...)))))), a continued fraction.
Original entry on oeis.org
1, 2, 7, 33, 185, 1170, 8121, 60846, 486753, 4125852, 36846557, 345205559, 3381126995, 34524194712, 366635359887, 4041180951473, 46149726728969, 545161967955668, 6652026230285141, 83730953689450825, 1085924693069106823, 14494802798426546660, 198918641942013097723
Offset: 0
G.f. A(x) = 1 + 2*x + 7*x^2 + 33*x^3 + 185*x^4 + 1170*x^5 + 8121*x^6 + 60846*x^7 + 486753*x^8 + ...
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b:= proc(x, y) option remember; `if`(y<0 or y>x, 0,
`if`(x=0, 1, b(x-1, y-1)+b(x-1, y+1)+b(x-2, y)*(y+1)))
end:
a:= n-> b(2*n, 0):
seq(a(n), n=0..22); # Alois P. Heinz, Apr 12 2025
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nmax = 22; CoefficientList[Series[1/(1 - x + ContinuedFractionK[-x, 1 - (k + 1) x, {k, 1, nmax}]), {x, 0, nmax}], x]
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