A144741 -id:A144741 - cp's OEIS frontend

A144761 Integers n such that Phi(2, a(n)) = A144741(a(n)) > Phi(2, k) for 0 < k < a(n).

4, 6, 10, 12, 18, 24, 30, 36, 42, 54, 60, 78, 84, 90, 120, 150, 168, 180, 210, 240, 270, 300, 330, 390, 420, 510, 546, 570, 630, 780, 840, 990, 1050, 1170, 1260, 1320, 1470, 1650, 1680, 1890, 2100, 2310, 2730, 3150, 3360, 3570, 3990, 4290, 4620, 4830

Offset: 1

Reikku Kulon, Sep 20 2008

Subset of A065385.

The first three terms are semiprimes and the number of factors gradually increases. All except four and ten are multiples of six.

Cf. A051953, A065385, A144741, A144742

A144762 rad(A144761(n)).

Original entry on oeis.org

2, 6, 10, 6, 6, 6, 30, 6, 42, 6, 30, 78, 42, 30, 30, 30, 42, 30, 210, 30, 30, 30, 330, 390, 210, 510, 546, 570, 210, 390, 210, 330, 210, 390, 210, 330, 210, 330, 210, 210, 210, 2310, 2730, 210, 210, 3570, 3990, 4290, 2310, 4830

Offset: 1

Reikku Kulon, Sep 20 2008

Cf. A007947, A144741

A144763 core(A144761(n)).

Original entry on oeis.org

1, 6, 10, 3, 2, 6, 30, 1, 42, 6, 15, 78, 21, 10, 30, 6, 42, 5, 210, 15, 30, 3, 330, 390, 105, 510, 546, 570, 70, 195, 210, 110, 42, 130, 35, 330, 30, 66, 105, 210, 21, 2310, 2730, 14, 210, 3570, 3990, 4290, 1155, 4830

Offset: 1

Reikku Kulon, Sep 20 2008

Cf. A007913, A144741

A144765 Number of triprimes less than or equal to and not coprime to n.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 2, 0, 2, 1, 2, 0, 3, 0, 4, 2, 4, 0, 4, 1, 4, 3, 5, 0, 7, 0, 6, 4, 6, 3, 7, 0, 6, 4, 6, 0, 8, 0, 8, 7, 8, 0, 10, 2, 10, 6, 10, 0, 12, 5, 10, 6, 10, 0, 12, 0, 10, 8, 10, 5, 14, 0, 12, 8, 15, 0, 16, 0, 13, 12, 14, 6, 19, 0, 17, 10, 15, 0, 19, 7, 15, 10, 15, 0, 19, 6, 16

Offset: 1

Reikku Kulon, Sep 20 2008

Cf. A000010, A014612, A144741.

a(n) = sum(k=1, n, if (bigomega(k) == 3, gcd(k,n) != 1)); \\ Michel Marcus, Apr 15 2023

cp's OEIS Frontend

A144761 Integers n such that Phi(2, a(n)) = A144741(a(n)) > Phi(2, k) for 0 < k < a(n).

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A144762 rad(A144761(n)).

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A144763 core(A144761(n)).

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A144765 Number of triprimes less than or equal to and not coprime to n.

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