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A130221
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Number of partitions of n-set in which number of blocks of size 2k is odd (or zero) for every k.
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0
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1, 1, 2, 5, 12, 37, 158, 667, 2740, 13461, 74710, 412095, 2406880, 15450541, 103187698, 715323395, 5236160612, 40014337437, 318488475658, 2637143123027, 22603231117364, 201268520010153, 1855401760331982, 17624602999352535
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| E.g.f.: exp(sinh(x))*Product_{k>0} (1+sinh(x^(2*k)/(2*k)!)).
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EXAMPLE
| a(4)=12 because from the 15 (=A000110(4)) partitions of the 4-set {a,b,c,d} only the partitions ab|cd, ac|bd and ad|bc do not qualify.
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MAPLE
| g:=exp(sinh(x))*(product(1+sinh(x^(2*k)/factorial(2*k)), k=1..25)): gser:= series(g, x=0, 30): seq(factorial(n)*coeff(gser, x, n), n=0..23); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 28 2007
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CROSSREFS
| Cf. A000110, A102759.
Sequence in context: A003724 A138314 A115277 * A036782 A050237 A050258
Adjacent sequences: A130218 A130219 A130220 * A130222 A130223 A130224
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KEYWORD
| easy,nonn
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Aug 05 2007, Aug 05 2007
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 28 2007
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