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A203092 Triangular array read by rows.  T(n,k) is the number of partial functions on {1,2,...,n} that are endofunctions with no cycles of length > 1 that have exactly k components. 1

%I

%S 1,1,1,1,4,1,1,18,9,1,1,116,78,16,1,1,1060,810,220,25,1,1,12702,10335,

%T 3260,495,36,1,1,187810,158613,54740,9835,966,49,1,1,3296120,2854908,

%U 1046024,209510,24696,1708,64,1

%N Triangular array read by rows. T(n,k) is the number of partial functions on {1,2,...,n} that are endofunctions with no cycles of length > 1 that have exactly k components.

%C Row sums = A088957.

%C T(n,0)= 1, the empty function.

%C T(n,n)= 1, the identity function.

%C T(n,n-1)= n^2 (apparently).

%F E.g.f.: exp(x)*exp(y T(x)) where T(x) is the e.g.f. for A000169.

%e T(2,1)= 4 because there are 4 such partial functions on {1,2}: 1->1, 2->2, 1->1 2->1, 1->2 2->2,

%e 1

%e 1 1

%e 1 4 1

%e 1 18 9 1

%e 1 116 78 16 1

%e 1 1060 810 220 25 1

%e 1 12702 10335 3260 495 36 1

%t nn = 8; t = Sum[n^(n - 1) x^n/n!, {n, 1, nn}];

%t f[list_] := Select[list, # > 0 &];

%t Map[f, Range[0, nn]! CoefficientList[ Series[Exp[x] Exp[y t], {x, 0, nn}], {x, y}]] // Flatten

%Y Cf. A088956, A144289

%K nonn,tabl

%O 0,5

%A _Geoffrey Critzer_, Dec 29 2011

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Last modified April 1 14:52 EDT 2020. Contains 333163 sequences. (Running on oeis4.)