A249409
E.g.f.: Sum_{n>=0} x^n * (exp(n*x) - 1)^n.
Original entry on oeis.org
1, 0, 2, 3, 100, 965, 26166, 652687, 22791336, 942744105, 46394042410, 2686920755651, 179344249073628, 13675378594960381, 1179389058183817950, 114010570608973463895, 12267159489256485080656, 1459502985288809274179153, 190910980556047614953376594, 27316077853047666256173322603
Offset: 0
E.g.f.: A(x) = 1 + 2*x^2/2! + 3*x^3/3! + 100*x^4/4! + 965*x^5/5! +...
where the e.g.f. satisfies following series identity:
A(x) = 1 + x*(exp(x)-1) + x^2*(exp(2*x)-1)^2 + x^3*(exp(3*x)-1)^3 + x^4*(exp(4*x)-1)^4 + x^5*(exp(5*x)-1)^5 + x^6*(exp(6*x)-1)^6 +...
A(x) = 1/(1+x) + x*exp(x)/(1+x*exp(x))^2 + x^2*exp(4*x)/(1+x*exp(2*x))^3 + x^3*exp(9*x)/(1+x*exp(3*x))^4 + x^4*exp(16*x)/(1+x*exp(4*x))^5 + x^5*exp(25*x)/(1+x*exp(5*x))^6 + x^6*exp(36*x)/(1+x*exp(6*x))^7 +...
A(x) = 1/(x+1) + x*exp(-x)/(x+exp(-x))^2 + x^2*exp(-2*x)/(x+exp(-2*x))^3 + x^3*exp(-3*x)/(x+exp(-3*x))^4 + x^4*exp(-4*x)/(x+exp(-4*x))^5 + x^5*exp(-5*x)/(x+exp(-5*x))^6 + x^6*exp(-6*x)/(x+exp(-6*x))^7 +...
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{a(n)=local(A=1); A=sum(k=0, n, x^k * (exp(k*x +x*O(x^n)) - 1)^k); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
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{a(n)=local(A=1); A=sum(k=0, n, x^k * exp(k^2*x +x*O(x^n)) / (1 + x*exp(k*x +x*O(x^n)))^(k+1) ); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
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{a(n)=local(A=1); A=sum(k=0, n, x^k * exp(-k*x +x*O(x^n)) / (x + exp(-k*x +x*O(x^n)))^(k+1) ); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
A351281
a(n) = Sum_{k=0..n} k! * k^k * Stirling2(n,k).
Original entry on oeis.org
1, 1, 9, 187, 7173, 440611, 39631509, 4910795107, 802015652853, 166948755155971, 43146953460348309, 13555255072473665827, 5087595330217093070133, 2248298922174973220446531, 1155512971750307157457879509, 683392198848998191062416885347
Offset: 0
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a[0] = 1; a[n_] := Sum[k! * k^k * StirlingS2[n, k], {k, 1, n}]; Array[a, 16, 0] (* Amiram Eldar, Feb 06 2022 *)
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a(n) = sum(k=0, n, k!*k^k*stirling(n, k, 2));
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my(N=20, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, (k*(exp(x)-1))^k)))
A121936
Number of digraphs with labeled vertices and labeled arcs, with n arcs and with no vertex of indegree 0 or outdegree 0.
Original entry on oeis.org
1, 0, 2, 18, 518, 23610, 1600982, 150451098, 18694217558, 2966151496410, 584994048653462, 140357794553191578, 40253455215544778198, 13598018000464234802010, 5343837921922909297592342
Offset: 0
A227207
E.g.f.: Sum_{n>=0} n^n * x^n / (n! * Product_{k=0..n} (1 - n*k*x)).
Original entry on oeis.org
1, 1, 6, 105, 3568, 204745, 18028266, 2278860535, 394667414016, 90302033890953, 26525942216131330, 9775058594870836861, 4433256936788979640848, 2434899483389881601250937, 1597444746833206096334387802, 1237091666097626095124512681755, 1119205949224015886848972396596736
Offset: 0
E.g.f.: A(x) = 1 + x + 6*x^2/2! + 105*x^3/3! + 3568*x^4/4! + 204745*x^5/5! +...
where
A(x) = 1 + x/(1-x) + 2^2*x^2/(2!*(1-2*1*x)*(1-2*2*x)) + 3^3*x^3/(3!*(1-3*1*x)*(1-3*2*x)*(1-3*3*x)) + 4^4*x^4/(4!*(1-4*1*x)*(1-4*2*x)*(1-4*3*x)*(1-4*4*x)) +...
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Flatten[{1,Table[n! * Sum[k^n * StirlingS2[n,k] / k!,{k,0,n}],{n,1,20}]}] (* Vaclav Kotesovec, May 08 2014 *)
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{a(n)=n!*polcoeff(sum(m=0, 20, m^m*x^m/m!/prod(k=1, m, 1-m*k*x +x*O(x^n))), n)}
for(n=0, 20, print1(a(n), ", "))
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{a(n)=n!^2*polcoeff(sum(m=0, n, (exp(m*x+x*O(x^n))-1)^m/m!^2), n)}
for(n=0, 20, print1(a(n), ", "))
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{a(n)=n!*sum(k=0, n, k^n*stirling(n, k, 2)/k!)}
for(n=0, 20, print1(a(n), ", "))
A351334
a(n) = Sum_{k=0..n} k! * (-k)^k * Stirling2(n,k).
Original entry on oeis.org
1, -1, 7, -139, 5227, -317491, 28352347, -3495615859, 568791063547, -118065959980051, 30445266606199387, -9547490385298102579, 3578014749635903623867, -1579193384981544127824211, 810752966831581612807206427, -479049438742420410992820125299
Offset: 0
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a(n) = sum(k=0, n, k!*(-k)^k*stirling(n, k, 2));
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my(N=20, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, (k*(1-exp(x)))^k)))