A178682
The number of functions f:{1,2,...,n}->{1,2,...,n} such that the number of elements that are mapped to m is divisible by m.
Original entry on oeis.org
1, 1, 2, 5, 13, 42, 150, 576, 2266, 9966, 47466, 237019, 1224703, 6429152, 35842344, 212946552, 1325810173, 8488092454, 55276544436, 362961569008, 2465240278980, 17538501945077, 130454679958312, 1002493810175093, 7838007702606372, 61789072382062638
Offset: 0
a(3) = 5 because there are 5 such functions: (1,1,1), (1,2,2), (2,1,2), (2,2,1), (3,3,3).
G.f. = 1 + x + 2*x^2 + 5*x^3 + 13*x^4 + 42*x^5 + 150*x^6 + 576*x^7 + ...
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m:=25; R:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!( (&*[(&+[x^(k*j)/Factorial(k*j): k in [0..m]]): j in [1..m]]) )); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Jan 26 2019
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b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
add(b(n-i*j, i-1)*binomial(n, i*j), j=0..n/i)))
end:
a:= n-> b(n$2):
seq(a(n), n=0..30); # Alois P. Heinz, Aug 30 2015
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Range[0,20]! CoefficientList[Series[Product[Sum[x^(j i)/(j i)!,{i,0,20}],{j,1,20}],{x,0,20}],x]
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m=30; my(x='x+O('x^m)); Vec(serlaplace(prod(j=1, m, sum(k=0,m, x^(k*j)/(k*j)!)))) \\ G. C. Greubel, Jan 26 2019
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m = 30; T = taylor(product(sum(x^(k*j)/factorial(k*j) for k in (0..m)) for j in (1..m)), x, 0, m); [factorial(n)*T.coefficient(x, n) for n in (0..m)] # G. C. Greubel, Jan 26 2019
A364310
Number T(n,k) of partitions of n into k parts where each block of part i with multiplicity j is marked with a word of length i*j over an n-ary alphabet whose letters appear in alphabetical order and all n letters occur exactly once in the partition; triangle T(n,k), n>=0, 0<=k<=n, read by rows.
Original entry on oeis.org
1, 0, 1, 0, 1, 1, 0, 1, 3, 1, 0, 1, 5, 6, 1, 0, 1, 15, 15, 10, 1, 0, 1, 22, 76, 35, 15, 1, 0, 1, 63, 168, 252, 70, 21, 1, 0, 1, 93, 574, 785, 658, 126, 28, 1, 0, 1, 255, 2188, 3066, 2739, 1470, 210, 36, 1, 0, 1, 386, 5490, 18235, 12181, 7857, 2940, 330, 45, 1
Offset: 0
T(4,1) = 1: 4abcd.
T(4,2) = 5: 3abc1d, 3abd1c, 3acd1b, 3bcd1a, 22abcd.
T(4,3) = 6: 2ab11cd, 2ac11bd, 2ad11bc, 2bc11ad, 2bd11ac, 2cd11ab.
T(4,4) = 1: 1111abcd.
Triangle T(n,k) begins:
1;
0, 1;
0, 1, 1;
0, 1, 3, 1;
0, 1, 5, 6, 1;
0, 1, 15, 15, 10, 1;
0, 1, 22, 76, 35, 15, 1;
0, 1, 63, 168, 252, 70, 21, 1;
0, 1, 93, 574, 785, 658, 126, 28, 1;
0, 1, 255, 2188, 3066, 2739, 1470, 210, 36, 1;
...
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b:= proc(n, i) option remember; expand(`if`(n=0, 1, `if`(i<1, 0,
add(b(n-i*j, i-1)*x^j*binomial(n, i*j), j=0..n/i))))
end:
T:= n-> (p-> seq(coeff(p, x, i), i=0..n))(b(n$2)):
seq(T(n), n=0..12);
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b[n_, i_] := b[n, i] = Expand[If[n == 0, 1, If[i < 1, 0,
Sum[b[n - i*j, i - 1]*x^j*Binomial[n, i*j], {j, 0, n/i}]]]];
T[n_] := CoefficientList[b[n, n], x];
Table[T[n], {n, 0, 12}] // Flatten (* Jean-François Alcover, Nov 18 2023, after Alois P. Heinz *)
A364322
Number of partitions of 2n with largest part n where each block of part i with multiplicity j is marked with a word of length i*j over a (2n)-ary alphabet whose letters appear in alphabetical order and all 2n letters occur exactly once in the partition.
Original entry on oeis.org
1, 1, 7, 81, 841, 10333, 137677, 1973401, 29150551, 484498301, 8769443541, 167200081777, 3311785261513, 66867027890601, 1437872937193801, 33031740883673521, 796918495251727081, 19807865344255857661, 501642119664087055501, 12828972405814319046601
Offset: 0
a(2) = 7: 2ab11cd, 2ac11bd, 2ad11bc, 2bc11ad, 2bd11ac, 2cd11ab, 22abcd.
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b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
add(b(n-i*j, i-1)*binomial(n, i*j), j=0..n/i)))
end:
a:= n-> b(2*n, n)-`if`(n=0, 0, b(2*n, n-1)):
seq(a(n), n=0..23);
Showing 1-3 of 3 results.
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