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A268667 Number of sequences with j copies of j for each j in {1,2,...,n} and longest increasing subsequence of length n. 2
1, 1, 2, 26, 3511, 6742796, 233249911607, 175703195017370516, 3377940832101159287907151, 1899957346851645870857879683505890, 35246706696124014829643459097288501560957174, 23998872279553738609365779286317516184675391844037227392 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
Sequences counted by a(n) have length A000217(n) and element sum A000330(n).
LINKS
J. D. Horton and A. Kurn, Counting sequences with complete increasing subsequences, Congressus Numerantium, 33 (1981), 75-80. MR 681905
EXAMPLE
a(2) = 2: 122, 212.
a(3) = 26: 122333, 123233, 123323, 123332, 132233, 132323, 132332, 133223, 133232, 212333, 213233, 213323, 231233, 231323, 233123, 312233, 312323, 312332, 313223, 313232, 321233, 321323, 323123, 331223, 331232, 332123.
MAPLE
g:= proc(l) option remember; (n-> f(l[1..nops(l)-1])*
binomial(n-1, l[-1]-1)+ add(f(sort(subsop(j=l[j]
-1, l))), j=1..nops(l)-1))(add(i, i=l))
end:
f:= l-> (n-> `if`(n<2 or l[-1]=1, 1, `if`(l[1]=0, 0, `if`(
n=2, binomial(l[1]+l[2], l[1])-1, g(l)))))(nops(l)):
a:= n-> f([$1..n]):
seq(a(n), n=0..8);
MATHEMATICA
g[l_] := g[l] = Function[n, f[Most[l]]*Binomial[n-1, l[[-1]]-1] + Sum[f[ Sort[ ReplacePart[l, j -> l[[j]]-1]]], {j, 1, Length[l]-1}]][Total[l]];
f[l_] := Function[n, If[n<2 || l[[-1]]==1, 1, If[l[[1]]==0, 0, If[n==2, Binomial[l[[1]] + l[[2]], l[[1]]]-1, g[l]]]]][Length[l]];
a[n_] := f[Range[n]];
Table[a[n], {n, 0, 11}] (* Jean-François Alcover, Feb 27 2017, after Alois P. Heinz *)
CROSSREFS
Sequence in context: A159318 A318132 A134795 * A330032 A273381 A094680
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 10 2016
STATUS
approved

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Last modified April 23 00:50 EDT 2024. Contains 371906 sequences. (Running on oeis4.)