cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A322428 Sum T(n,k) of k-th largest parts of all compositions of n; triangle T(n,k), n>=1, 1<=k<=n, read by rows.

Original entry on oeis.org

1, 3, 1, 8, 3, 1, 19, 8, 4, 1, 43, 20, 11, 5, 1, 94, 48, 27, 16, 6, 1, 202, 110, 64, 42, 22, 7, 1, 428, 245, 149, 100, 64, 29, 8, 1, 899, 533, 341, 228, 163, 93, 37, 9, 1, 1875, 1142, 765, 512, 383, 256, 130, 46, 10, 1, 3890, 2420, 1683, 1144, 859, 638, 386, 176, 56, 11, 1
Offset: 1

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Author

Alois P. Heinz, Dec 07 2018

Keywords

Examples

			The 4 compositions of 3 are: 111, 12, 21, 3.  The sums of k-th largest parts for k=1..3 give: 1+2+2+3 = 8, 1+1+1+0 = 3, 1+0+0+0 = 1.
Triangle T(n,k) begins:
     1;
     3,    1;
     8,    3,   1;
    19,    8,   4,   1;
    43,   20,  11,   5,   1;
    94,   48,  27,  16,   6,   1;
   202,  110,  64,  42,  22,   7,   1;
   428,  245, 149, 100,  64,  29,   8,  1;
   899,  533, 341, 228, 163,  93,  37,  9,  1;
  1875, 1142, 765, 512, 383, 256, 130, 46, 10, 1;
  ...
		

Crossrefs

Column k=1 gives A102712.
Row sums give A001787.
T(n+1,1+ceiling(n/2)) gives A027306.
Cf. A322427.

Programs

  • Maple
    b:= proc(n, l) option remember; `if`(n=0, add(l[-i]*x^i,
          i=1..nops(l)), add(b(n-j, sort([l[], j])), j=1..n))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=1..degree(p)))(b(n, [])):
    seq(T(n), n=1..12);
  • Mathematica
    b[n_, l_] := b[n, l] = If[n == 0, Sum[l[[-i]] x^i, {i, 1, Length[l]}], Sum[b[n - j, Sort[Append[l, j]]], {j, 1, n}]];
    T[n_] := Function[p, Table[Coefficient[p, x, i], {i, 1, Exponent[p, x]}]][ b[n, {}]];
    Array[T, 12] // Flatten (* Jean-François Alcover, Dec 29 2018, after Alois P. Heinz *)