A381398 Irregular triangle read by rows, where row n lists the elements of the set of bases and exponents (including exponents = 1) in the prime factorization of n.
1, 2, 1, 3, 2, 1, 5, 1, 2, 3, 1, 7, 2, 3, 2, 3, 1, 2, 5, 1, 11, 1, 2, 3, 1, 13, 1, 2, 7, 1, 3, 5, 2, 4, 1, 17, 1, 2, 3, 1, 19, 1, 2, 5, 1, 3, 7, 1, 2, 11, 1, 23, 1, 2, 3, 2, 5, 1, 2, 13, 3, 1, 2, 7, 1, 29, 1, 2, 3, 5, 1, 31, 2, 5, 1, 3, 11, 1, 2, 17, 1, 5, 7, 2, 3
Offset: 2
Examples
Triangle begins:
[2] 1, 2;
[3] 1, 3;
[4] 2;
[5] 1, 5;
[6] 1, 2, 3;
[7] 1, 7;
[8] 2, 3;
[9] 2, 3;
[10] 1, 2, 5;
...
The prime factorization of 10 is 2^1*5^1 and the set of these bases and exponents is {1, 2, 5}.
Links
- Paolo Xausa, Table of n, a(n) for n = 2..10326 (rows 2..3000 of triangle, flattened).