

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.


2



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
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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: A225176 A118665 A225243 * A027746 A240230 A238689
Adjacent sequences: A207335 A207336 A207337 * A207339 A207340 A207341


KEYWORD

sign,tabf


AUTHOR

Omar E. Pol, Apr 15 2012


STATUS

approved



