A130208 Diagonalized matrix of A000203, sigma(n).

1, 0, 3, 0, 0, 4, 0, 0, 0, 7, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 12, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 15, 0, 0, 0, 0, 0, 0, 0, 0, 13, 0, 0, 0, 0, 0, 0, 0, 0, 0, 18, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 28, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 24

Offset: 1

Author

Gary W. Adamson, May 16 2007

Keywords

• nonn
• tabl

Comments

A130207 replaces sigma(n) with phi(n), A000010. A130209 replaces sigma(n) with d(n), A000005.

Examples

			First few rows of the triangle are:
1;
0, 3;
0, 0, 4;
0, 0, 0, 7;
0, 0, 0, 0, 6;
0, 0, 0, 0, 0, 12;
...
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..22155; the first 210 rows of the triangle

Crossrefs

Cf. A000203, A130207, A130209.

Programs

PARI

for(n=1,9,for(k=2,n,print1("0, "));print1(sigma(n)", ")) \\ Charles R Greathouse IV, Feb 14 2013

PARI

A130208(n) = if(ispolygonal(n,3), sigma((sqrtint(1+(n*8))-1)/2), 0); \\ Antti Karttunen, Jan 17 2025

Formula

Infinite lower triangular matrix with A000203, sigma(n), in the main diagonal and the rest zeros.

Extensions

Data section extended up to a(120) by Antti Karttunen, Jan 17 2025