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Search: id:A105486
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| A105486 |
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Number of partitions of {1...n} containing 4 strings of 3 consecutive integers, where each string is counted within a block, and a string of more than 3 consecutive integers are counted three at a time. |
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+0
5
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| 1, 2, 11, 50, 255, 1362, 7746, 46556, 294965, 1963865, 13703812, 99974851, 760824922, 6027441398, 49616033975, 423649629415, 3746306203604, 34259548971914, 323564415957687, 3152120868598090, 31638011553779137
(list; graph; listen)
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OFFSET
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6,2
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REFERENCES
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A. O. Munagi, Set Partitions with Successions and Separations, Int. J. Math and Math. Sc. 2005, no. 3 (2005), 451-463.
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LINKS
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A. O. Munagi, Set Partitions with Successions and Separations,IJMMS 2005:3 (2005),451-463.
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FORMULA
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a(n)=Sum(c(n, k, 4), k=1...n), where c(n, k, 4) is the case r=4 of c(n, k, r) given by c(n, k, r)=c(n-1, k-1, r)+(k-1)c(n-1, k, r)+c(n-2, k-1, r)+(k-1)c(n-2, k, r)+c(n-1, k, r-1)-c(n-2, k-1, r-1)-(k-1)c(n-2, k, r-1), r=0, 1, .., n-k-1, k=1, 2, .., n-2r, c(n, k, 0)=sum(binomial(n-j, j)*S2(n-j-1, k-1), j= 0..floor(n/2)).
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EXAMPLE
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a(7) = 2 because the partitions of {1,...,7} with 4 strings of 3 consecutive integers are 123456/7, 1/234567.
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MAPLE
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c := proc(n, k, r) option remember ; local j ; if r =0 then add(binomial(n-j, j)*combinat[stirling2](n-j-1, k-1), j=0..floor(n/2)) ; else if r <0 or r > n-k-1 then RETURN(0) fi ; if n <1 then RETURN(0) fi ; if k <1 then RETURN(0) fi ; RETURN( c(n-1, k-1, r)+(k-1)*c(n-1, k, r)+c(n-2, k-1, r)+(k-1)*c(n-2, k, r) +c(n-1, k, r-1)-c(n-2, k-1, r-1)-(k-1)*c(n-2, k, r-1) ) ; fi ; end: A105486 := proc(n) local k ; add(c(n, k, 4), k=1..n) ; end: for n from 6 to 29 do printf("%d, ", A105486(n)) ; od ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 20 2007
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CROSSREFS
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Cf. A105485, A105487, A105490, A105494.
Adjacent sequences: A105483 A105484 A105485 this_sequence A105487 A105488 A105489
Sequence in context: A034568 A036996 A108851 this_sequence A137960 A018933 A116586
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KEYWORD
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nonn
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AUTHOR
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A. O. Munagi (amunagi(AT)yahoo.com), Apr 10 2005
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 20 2007
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