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A274869 Number of set partitions of [n] into exactly five blocks such that all odd elements are in blocks with an odd index and all even elements are in blocks with an even index. 2
1, 2, 13, 26, 113, 226, 833, 1666, 5649, 11298, 36561, 73122, 230161, 460322, 1424401, 2848802, 8720657, 17441314, 53021969, 106043938, 320925969, 641851938, 1936736529, 3873473058, 11665150225, 23330300450, 70169841937, 140339683874, 421734846737 (list; graph; refs; listen; history; text; internal format)
OFFSET
5,2
LINKS
FORMULA
G.f.: x^5/((x-1)*(2*x-1)*(x+1)*(6*x^2-1)*(2*x^2-1)).
EXAMPLE
a(6) = 2: 1|26|3|4|5, 1|2|3|46|5.
a(7) = 13: 13|24|5|6|7, 15|24|3|6|7, 1|24|35|6|7, 15|26|3|4|7, 15|2|3|46|7, 1|26|35|4|7, 1|2|35|46|7, 17|26|3|4|5, 1|26|37|4|5, 1|26|3|4|57, 17|2|3|46|5, 1|2|37|46|5, 1|2|3|46|57.
CROSSREFS
Column k=5 of A274537.
Sequence in context: A018745 A117983 A367265 * A018400 A091052 A294555
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Jul 09 2016
STATUS
approved

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Last modified June 17 06:18 EDT 2024. Contains 373432 sequences. (Running on oeis4.)