A337209 Triangle read by rows T(n,k), (n >= 1, k > = 1), in which row n has length A000070(n-1) and every column gives A000203, the sum of divisors function.

1, 3, 1, 4, 3, 1, 1, 7, 4, 3, 3, 1, 1, 1, 6, 7, 4, 4, 3, 3, 3, 1, 1, 1, 1, 1, 12, 6, 7, 7, 4, 4, 4, 3, 3, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1, 8, 12, 6, 6, 7, 7, 7, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 15, 8, 12, 12, 6, 6, 6, 7, 7, 7, 7, 7, 4, 4, 4, 4, 4, 4, 4

Offset: 1

Author

Omar E. Pol, Nov 27 2020

Keywords

• nonn
• tabf

Comments

Conjecture: the sum of row n equals A066186(n), the sum of all parts of all partitions of n.

Examples

			Triangle begins:
   1;
   3,  1;
   4,  3, 1, 1;
   7,  4, 3, 3, 1, 1, 1;
   6,  7, 4, 4, 3, 3, 3, 1, 1, 1, 1, 1;
  12,  6, 7, 7, 4, 4, 4, 3, 3, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1;
   8, 12, 6, 6, 7, 7, 7, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, 1, ...
  ...
		

Links

• Paolo Xausa, Table of n, a(n) for n = 1..10980 (rows 1..21 of the triangle, flattened)

Crossrefs

Sum of divisors of terms of A176206.

Cf. A339278 (another version).

Cf. A000070, A000203, A066186, A221529, A238442, A339258.

Programs

Mathematica

A337209row[n_]:=Flatten[Table[ConstantArray[DivisorSigma[1,n-m],PartitionsP[m]],{m,0,n-1}]];Array[A337209row,10] (* Paolo Xausa, Sep 02 2023 *)

PARI

f(n) = sum(k=0, n-1, numbpart(k));
T(n, k) = {if (k > f(n), error("invalid k")); if (k==1, return (sigma(n))); my(s=0); while (k <= f(n-1), s++; n--;); sigma(1+s);}
tabf(nn) = {for (n=1, nn, for (k=1, f(n), print1(T(n,k), ", ");); );} \\ Michel Marcus, Jan 13 2021

Formula

T(n,k) = A000203(A176206(n,k)).