A261215 Triangle read by rows: T(n, k) is the number of squarefree integers x such that x<=primorial(n) and omega(n) = k with 0<=k<=n.

1, 1, 1, 1, 3, 1, 1, 10, 7, 1, 1, 46, 62, 19, 1, 1, 343, 643, 359, 58, 1, 1, 3248, 7429, 5723, 1708, 152, 1, 1, 42331, 110373, 104928, 44365, 7926, 422, 1, 1, 646029, 1848729, 2024368, 1068664, 276833, 31108, 995, 1

Offset

0,5

Links

Giovanni Resta, Table of n, a(n) for n = 0..77

Example

Triangle begins:
1;
1, 1;
1, 3, 1;
1, 10, 7, 1;
1, 46, 62, 19, 1;
1, 343, 643, 359, 58, 1;
...

Prog

(PARI) primo(n) = prod(i=1, n, prime(i));
tabl(nn) = {v = vector(1); na = 1; for (n=0, nn, nb = primo(n); for (i=na, primo(n), if (issquarefree(i), v[1+omega(i)]++); ); print(v); v = concat(v, 0); na = nb + 1; ); }

Crossrefs

Cf. A002110 (primorials), A000849 (1st column), A001221 (omega), A005117 (squarefrees), A092479 (similar triangle).

Sequence in context: A060543 A267751 A185996 * A176157 A176156 A172339

Adjacent sequences: A261212 A261213 A261214 * A261216 A261217 A261218

Keyword

nonn,tabl

Author

Michel Marcus, Aug 12 2015

Status

approved