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

1,2

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.

Links

Table of n, a(n) for n=1..77.

Example

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.

Sequence in context: A333238 A336526 A225243 * A027746 A307746 A348477

Adjacent sequences: A207335 A207336 A207337 * A207339 A207340 A207341

Keyword

sign,tabf

Author

Omar E. Pol, Apr 15 2012

Status

approved