A307746 Triangle read by rows, obtained by omitting all the 1's from the triangle in A307641 (except for the first row).

1, 2, 3, 2, 2, 5, 2, 3, 7, 2, 2, 2, 3, 3, 2, 5, 11, 2, 3, 2, 13, 2, 7, 3, 5, 2, 2, 2, 2, 17, 2, 3, 3, 19, 2, 2, 5, 3, 7, 2, 11, 23, 2, 3, 2, 2, 5, 5, 2, 13, 3, 3, 3, 2, 2, 7, 29, 2, 3, 5, 31, 2, 2, 2, 2, 2, 3, 11, 2, 17, 5, 7, 2, 3, 2, 3, 37, 2, 19, 3, 13

Offset: 1

Author

I. V. Serov, Apr 26 2019

Keywords

• nonn
• tabf

Comments

Has same shape as the triangle in A027746. The first difference occurs at row 12.

Examples

			Triangle begins:
1;
2;
3;
2, 2;
5;
2, 3;
7;
2, 2, 2;
3, 3;
2, 5;
11;
2, 3, 2;
...
		

Links

• Michel Marcus, Rows n=1..3000 of triangle, flattened (first 131 rows from I. V. Serov)

Crossrefs

Cf. A088387, A014963, A027746, A307641.

Programs

PARI

f(n)=ispower(n, , &n); if(isprime(n), n, 1); \\ A014963
row(n) = if (n==1, [1], my(d=divisors(n)); select(x->x!=1, vector(#d, k, f(d[k]))));
tabl(nn) = for (n=1, nn, print(row(n))); \\ Michel Marcus, Apr 27 2019

Formula

Row(i) = {d|i, A014963(d) > 1} A014963(d).

For i > 1, T(i, A001222(i)) = A088387(i). This is the last term of the i-th row.