The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A333061 Number of entries in the fourth blocks of all set partitions of [n] when blocks are ordered by decreasing lengths. 2
 1, 11, 81, 512, 3151, 20071, 133853, 924320, 6551293, 47529561, 354259153, 2725545695, 21741995463, 180198265559, 1551865576121, 13865702570254, 128238585735637, 1224733005946425, 12053244176971825, 122035994844818345, 1269623551116437475, 13561114665253219451 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 4..576 Wikipedia, Partition of a set MAPLE b:= proc(n, i, t) option remember; `if`(n=0, [1, 0], `if`(i<1, 0, add((p-> p+`if`(t>0 and t-j<1, [0, p[1]*i], 0))( combinat[multinomial](n, i\$j, n-i*j)/j!* b(n-i*j, min(n-i*j, i-1), max(0, t-j))), j=0..n/i))) end: a:= n-> b(n\$2, 4)[2]: seq(a(n), n=4..25); MATHEMATICA multinomial[n_, k_List] := n!/Times @@ (k!); b[n_, i_, t_] := b[n, i, t] = If[n == 0, {1, 0}, If[i < 1, {0, 0}, Sum[Function[p, p + If[t > 0 && t - j < 1, {0, p[[1]]*i}, {0, 0}]][ multinomial[n, Append[Table[i, {j}], n - i*j]]/j!* b[n - i*j, Min[n - i*j, i - 1], Max[0, t - j]]], {j, 0, n/i}]]]; a[n_] := b[n, n, 4][[2]]; a /@ Range[4, 25] (* Jean-François Alcover, Apr 24 2021, after Alois P. Heinz *) CROSSREFS Column k=4 of A319375. Sequence in context: A210064 A323223 A211557 * A055429 A227556 A181989 Adjacent sequences: A333058 A333059 A333060 * A333062 A333063 A333064 KEYWORD nonn AUTHOR Alois P. Heinz, Mar 06 2020 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 23 20:00 EDT 2024. Contains 373653 sequences. (Running on oeis4.)