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A086364 Triangle read by rows: S_D(n,k) = `Type D' Stirling numbers of the second kind. 2
1, 2, 2, 2, 9, 4, 2, 27, 36, 10, 2, 65, 195, 140, 26, 2, 143, 840, 1180, 540, 76, 2, 301, 3171, 7735, 6510, 2142, 232, 2, 619, 11060, 43659, 59920, 34692, 8624, 764, 2, 1257, 36707, 223566, 467691, 423612, 180852, 35856, 2620, 2, 2535, 117960, 1071350 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..48.

FORMULA

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}.

CROSSREFS

Cf. A085483, A086365 (row sums).

Sequence in context: A138056 A022459 A060804 * A260662 A228044 A171529

Adjacent sequences:  A086361 A086362 A086363 * A086365 A086366 A086367

KEYWORD

easy,nonn,tabl

AUTHOR

James East, Sep 04 2003

STATUS

approved

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Last modified November 18 12:20 EST 2017. Contains 294891 sequences.