A389215 Numbers k such that {sum of unitary divisors of k} plus {sum of squarefree divisors of k} >= 2*k.

1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 26, 28, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 46, 47, 51, 52, 53, 55, 57, 58, 59, 60, 61, 62, 65, 66, 67, 68, 69, 70, 71, 73, 74, 76, 77, 78, 79, 82, 83, 84, 85, 86, 87, 89, 90, 91, 92, 93, 94, 95, 97, 101, 102, 103, 105, 106

Offset

1,2

Comments

Numbers k for which A325973(k) >= k, or equally, A325977(k) >= 0.

{k | A034448(k)+A048250(k) >= 2*k}.

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Prog

(PARI)
A325973(n) = (1/2)*sumdiv(n, d, d*(issquarefree(d) + (1==gcd(d, n/d))));
is_A389215(k) = (A325973(k) >= k);

Crossrefs

Cf. A034448, A048250, A325973, A388986 (complement).

Positions of nonnegative terms in A325977.

Subsequences: (A005117 U A389216), A325963, A389079.

Sequence in context: A350076 A379396 A393981 * A035060 A231272 A143719

Adjacent sequences: A389212 A389213 A389214 * A389216 A389217 A389218

Keyword

nonn

Author

Antti Karttunen, Sep 30 2025

Status

approved