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A136568
Irregular triangle read by rows: row n contains the distinct values (in numerical order) making up the nonzero exponents in the prime factorization of n. (Row 1 = (0).).
5
0, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 3, 2, 1, 3, 1, 2, 1, 1, 1, 5, 1, 1, 1, 2, 1, 1, 1, 1, 3, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 4, 2, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 2, 1, 1, 1, 2, 6, 1, 1, 1, 1, 2, 1, 1
OFFSET
1,4
COMMENTS
Row n, for n>=2, contains A071625(n) terms.
EXAMPLE
4200 = 2^3 * 3^1 * 5^2 * 7^1. The exponents of the prime factorization are therefore 3,1,2,1. Therefore row 4200 is (1,2,3).
Table begins:
0;
1;
1;
2;
1;
1;
1;
3;
2;
1;
1;
1, 2;
MATHEMATICA
Join[{0}, Flatten[Rest[Table[Union[Transpose[FactorInteger[n]][[2]]], {n, 100}]]]] (* Harvey P. Dale, Mar 19 2013 *)
PROG
(PARI) row(n) = if(n == 1, [0], Set(factor(n)[, 2])); \\ Amiram Eldar, Aug 04 2024
CROSSREFS
Sequence in context: A359165 A377364 A086290 * A342477 A372287 A152157
KEYWORD
nonn,tabf
AUTHOR
Leroy Quet, Jan 07 2008
EXTENSIONS
More terms from Harvey P. Dale, Mar 19 2013
STATUS
approved