A207338 Triangle read by rows in which row n lists the prime factors of n with repetition, with a(1) = 1, but with the primes of the form 4k + 1 multiplied by -1.

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

Offset: 1

Author

Omar E. Pol, Apr 15 2012

Keywords

• sign
• tabf

Comments

The row products of triangle give A209662. Also the row products of triangle divided by n give A209661. The mentioned sequences are related to an infinite series which is equal to pi, due to Leonhard Euler.

Examples

			Written as a triangle begins:
1;
2;
3;
2, 2;
-5;
2, 3;
7;
2, 2, 2;
3, 3;
2, -5;
11;
2, 2, 3;
-13;
2, 7;
3, -5;
2, 2, 2, 2;
		

Crossrefs

Absolute values give A027746.

Cf. A002144, A002145, A209661, A209662.