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Search: id:A013979
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| A013979 |
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Expansion of 1/(1-x^2-x^3-x^4). |
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+0
6
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| 1, 0, 1, 1, 2, 2, 4, 5, 8, 11, 17, 24, 36, 52, 77, 112, 165, 241, 354, 518, 760, 1113, 1632, 2391, 3505, 5136, 7528, 11032, 16169, 23696, 34729, 50897, 74594, 109322, 160220, 234813, 344136, 504355, 739169
(list; graph; listen)
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OFFSET
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0,5
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COMMENT
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For n>0, number of ordered partitions of n into 2's, 3's, and 4's. - Len Smiley (smiley(AT)math.uaa.alaska.edu), May 08 2001
Diagonal sums of trinomial triangle A071675 (Riordan array (1, x(1+x+x^2))). - Paul Barry (pbarry(AT)wit.ie), Feb 15 2005
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REFERENCES
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C. K. Fan, A Hecke algebra quotient and some combinatorial applications. J. Algebraic Combin. 5 (1996), no. 3, 175-189.
C. K. Fan, Structure of a Hecke algebra quotient. J. Amer. Math. Soc. 10 (1997), no. 1, 139-167. [Page 156, f^0_n.]
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FORMULA
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a(n)=sum{k=0..floor(n/2), sum{i=0..floor(n/2), C(k, 2i+3k-n)C(2i+3k-n, i)}}; - Paul Barry (pbarry(AT)wit.ie), Feb 15 2005
a(n) = a(n-4) + a(n-3) + a(n-2). - Jon Schoenfield (jonscho(AT)hiwaay.net), Aug 07 2006
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CROSSREFS
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Cf. A060945 (Ordered partitions into 1's, 2's, and 4's), A107458.
First differences of A023435.
Sequence in context: A109434 A089299 A017910 this_sequence A107458 A060280 A006206
Adjacent sequences: A013976 A013977 A013978 this_sequence A013980 A013981 A013982
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KEYWORD
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nonn
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AUTHOR
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njas
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