

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
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OFFSET

5,2


LINKS



FORMULA

G.f.: x^5/((x1)*(2*x1)*(x+1)*(6*x^21)*(2*x^21)).


EXAMPLE

a(6) = 2: 126345, 123465.
a(7) = 13: 1324567, 1524367, 1243567, 1526347, 1523467, 1263547, 1235467, 1726345, 1263745, 1263457, 1723465, 1237465, 1234657.


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



STATUS

approved



