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.

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A324939 Triangle T(n,k) read by rows in which n-th row lists in increasing order all compositions [c_1, c_2, ..., c_q] of n encoded as Product_{i=1..q} prime(i)^(c_i); n>=0, 1<=k<=A011782(n).

Original entry on oeis.org

1, 2, 4, 6, 8, 12, 18, 30, 16, 24, 36, 54, 60, 90, 150, 210, 32, 48, 72, 108, 120, 162, 180, 270, 300, 420, 450, 630, 750, 1050, 1470, 2310, 64, 96, 144, 216, 240, 324, 360, 486, 540, 600, 810, 840, 900, 1260, 1350, 1500, 1890, 2100, 2250, 2940, 3150, 3750, 4410, 4620, 5250, 6930, 7350, 10290, 11550, 16170, 25410, 30030
Offset: 0

Views

Author

Alois P. Heinz, Sep 04 2019

Keywords

Comments

All terms sorted give A055932.
All terms first sorted by number of factors give A057335.

Examples

			Triangle T(n,k) begins:
   1;
   2;
   4,  6;
   8, 12, 18,  30;
  16, 24, 36,  54,  60,  90, 150, 210;
  32, 48, 72, 108, 120, 162, 180, 270, 300, 420, 450, 630, 750, 1050, 1470, 2310;
  ...
		

Crossrefs

Column k=1 gives A000079.
Last elements of rows give A002110.
Row sums give A325054.
Row lengths give A011782.

Programs

  • Maple
    b:= n-> `if`(n=0, [[]], [seq(map(x-> [j, x[]], b(n-j))[], j=1..n)]):
    T:= n-> sort(map(x-> mul(ithprime(i)^x[i], i=1..nops(x)), b(n)))[]:
    seq(T(n), n=0..7);

A343751 A(n,k) is the sum of all compositions [c_1, c_2, ..., c_k] of n into k nonnegative parts encoded as Product_{i=1..k} prime(i)^(c_i); square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 2, 0, 1, 5, 4, 0, 1, 10, 19, 8, 0, 1, 17, 69, 65, 16, 0, 1, 28, 188, 410, 211, 32, 0, 1, 41, 496, 1726, 2261, 665, 64, 0, 1, 58, 1029, 7182, 14343, 11970, 2059, 128, 0, 1, 77, 2015, 20559, 93345, 112371, 61909, 6305, 256, 0, 1, 100, 3478, 54814, 360612, 1139166, 848506, 315850, 19171, 512, 0
Offset: 0

Views

Author

Alois P. Heinz, Apr 27 2021

Keywords

Examples

			A(1,3) = 10 = 5 + 3 + 2, sum of encoded compositions [0,0,1], [0,1,0], [1,0,0].
A(4,2) = 211 = 81 + 54 + 36 + 24 + 16, sum of encoded compositions [0,4], [1,3], [2,2], [3,1], [4,0].
Square array A(n,k) begins:
  1,  1,    1,     1,      1,        1,        1, ...
  0,  2,    5,    10,     17,       28,       41, ...
  0,  4,   19,    69,    188,      496,     1029, ...
  0,  8,   65,   410,   1726,     7182,    20559, ...
  0, 16,  211,  2261,  14343,    93345,   360612, ...
  0, 32,  665, 11970, 112371,  1139166,  5827122, ...
  0, 64, 2059, 61909, 848506, 13379332, 89131918, ...
		

Crossrefs

Columns k=0-4 give: A000007, A000079, A001047(n+1), A016273, A025931.
Rows n=0-2 give: A000012, A007504, A357251.
Main diagonal gives A332967.

Programs

  • Maple
    A:= proc(n, k) option remember; `if`(n=0, 1,
         `if`(k=0, 0, add(ithprime(k)^i*A(n-i, k-1), i=0..n)))
        end:
    seq(seq(A(n, d-n), n=0..d), d=0..10);
    # second Maple program:
    A:= proc(n, k) option remember; `if`(n=0, 1,
         `if`(k=0, 0, ithprime(k)*A(n-1, k)+A(n, k-1)))
        end:
    seq(seq(A(n, d-n), n=0..d), d=0..10);
  • Mathematica
    A[n_, k_] := A[n, k] = If[n == 0, 1,
         If[k == 0, 0, Prime[k] A[n-1, k] + A[n, k-1]]];
    Table[Table[A[n, d-n], {n, 0, d}], {d, 0, 10}] // Flatten (* Jean-François Alcover, Nov 06 2021, after 2nd Maple program *)

Formula

A(n,k) = [x^n] Product_{i=1..k} 1/(1-prime(i)*x).
A(n,k) = A124960(n+k,k) for k >= 1.
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