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Triangle read by rows: S_D(n,k) = `Type D' Stirling numbers of the second kind.
2

%I #5 Oct 12 2013 15:30:32

%S 1,2,2,2,9,4,2,27,36,10,2,65,195,140,26,2,143,840,1180,540,76,2,301,

%T 3171,7735,6510,2142,232,2,619,11060,43659,59920,34692,8624,764,2,

%U 1257,36707,223566,467691,423612,180852,35856,2620,2,2535,117960,1071350

%N Triangle read by rows: S_D(n,k) = `Type D' Stirling numbers of the second kind.

%F A partition of {-n, ..., -1, 1, ..., n} into nonempty subsets X_1, ..., X_r is called `symmetric' if for each i -X_i = X_j for some j. S_D(n, k) is the number of such symmetric partitions whose induced partition on {1, ..., n} involves k nonempty subsets and none of the X_i are of the form {j, -j}.

%Y Cf. A085483, A086365 (row sums).

%K easy,nonn,tabl

%O 0,2

%A _James East_, Sep 04 2003

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Last modified September 20 06:43 EDT 2024. Contains 376067 sequences. (Running on oeis4.)