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.

A224381 Table of coefficients in the expansion of product((1+d_i*x), d_i|n).

Original entry on oeis.org

1, 1, 1, 1, 3, 2, 1, 4, 3, 1, 7, 14, 8, 1, 6, 5, 1, 12, 47, 72, 36, 1, 8, 7, 1, 15, 70, 120, 64, 1, 13, 39, 27, 1, 18, 97, 180, 100, 1, 12, 11, 1, 28, 287, 1400, 3444, 4032, 1728, 1, 14, 13, 1, 24, 163, 336, 196, 1, 24, 158, 360, 225, 1, 31, 310, 1240, 1984, 1024
Offset: 0

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Author

Philippe Deléham, Apr 05 2013

Keywords

Examples

			Row n = 6 : 1, 12, 47, 72, 36 because  (1+x)*(1+2x)*(1+3x)*(1+6x) = 1 + 12*x + 47*x^2 + 72*x^3 + 36*x^4.
Table begins :
  1;
  1,  1;
  1,  3,   2;
  1,  4,   3;
  1,  7,  14,    8;
  1,  6,   5;
  1, 12,  47,   72,   36;
  1,  8,   7;
  1, 15,  70,  120,   64;
  1, 13,  39,   27;
  1, 18,  97,  180,  100;
  1, 12,  11;
  1, 28, 287, 1400, 3444, 4032, 1728;
  1, 14,  13;
  1, 24, 163,  336,  196;
  1, 24, 158,  360,  225;
  1, 31, 310, 1240, 1984, 1024;
  ...
		

Crossrefs

Columns k=0-3 give: A000012, A000203, A119616, A067817.
Row lengths are: A000005(n)+1.
Last elements of rows give: A007955.

Programs

  • Maple
    with(numtheory):
    T:= proc(n) local p;
          p:= mul(1+d*x, d=divisors(n));
          seq(coeff(p, x, k), k=0..degree(p))
        end:
    seq(T(n), n=0..30);  # Alois P. Heinz, Apr 05 2013
  • Mathematica
    T[n_] := CoefficientList[Product[1+d*x, {d, Divisors[n]}], x]; T[0] = {1};
    Array[T, 20, 0] // Flatten (* Jean-François Alcover, Mar 27 2017 *)

Formula

T(n,k) = [x^k] Product_{d|n} (1+d*x).