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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A257741 Number of multisets of nonempty words with a total of n letters over n-ary alphabet such that if a letter occurs in the multiset all predecessors occur at least once. 4
 1, 1, 5, 30, 241, 2356, 27315, 364319, 5488468, 92040141, 1698933390, 34206221161, 745622368096, 17486274798203, 438859174516837, 11732964019785027, 332818604033186036, 9981540739647177238, 315518234680527952625, 10482878954868309043158, 365158449014981632341391 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..400 FORMULA a(n) = Sum_{k=0..n} A257740(n,k). EXAMPLE a(0) = 1: {}. a(1) = 1: {a}. a(2) = 5: {a,a}, {aa}, {ab}, {ba}, {a,b}. MATHEMATICA A[n_, k_] := A[n, k] = If[n == 0, 1, Sum[DivisorSum[j, #*k^#&]*A[n - j, k], {j, 1, n}]/n]; T[n_, k_] := Sum[A[n, k - i]*(-1)^i*Binomial[k, i], {i, 0, k}]; a[n_] := Sum[T[n, k], {k, 0, n}]; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Jun 01 2022, after Alois P. Heinz in A257740 *) CROSSREFS Cf. A257740, A319518. Sequence in context: A144498 A201368 A072213 * A308946 A346681 A279155 Adjacent sequences: A257738 A257739 A257740 * A257742 A257743 A257744 KEYWORD nonn AUTHOR Alois P. Heinz, May 06 2015 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 December 1 15:30 EST 2023. Contains 367476 sequences. (Running on oeis4.)