A324534 -id:A324534 - cp's OEIS frontend

A324644 a(n) = gcd(sigma(n), A276086(n)).

1, 3, 2, 1, 6, 1, 2, 15, 1, 9, 6, 1, 2, 3, 6, 1, 18, 1, 10, 3, 2, 9, 6, 5, 1, 3, 10, 1, 30, 1, 2, 21, 6, 9, 6, 7, 2, 15, 14, 45, 42, 1, 2, 21, 6, 9, 6, 1, 1, 3, 6, 7, 18, 5, 2, 15, 10, 45, 30, 7, 2, 3, 2, 1, 42, 1, 2, 21, 6, 9, 18, 5, 2, 3, 2, 35, 6, 7, 10, 3, 1, 63, 42, 7, 2, 3, 30, 45, 90, 1, 14, 21, 2, 9, 6, 7, 98, 3, 6, 7, 6, 1, 2, 105, 6

Offset: 1

Antti Karttunen, Mar 11 2019

nonn

Antti Karttunen, Table of n, a(n) for n = 1..30030

Cf. A000203, A009194, A276086, A324198, A324534, A324645, A324646, A364286.

Cf. A088828 (positions of even terms), A176693 (of odd terms).

A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
A324644(n) = gcd(sigma(n),A276086(n));

a(n) = gcd(A000203(n), A276086(n)).

A374476 Composite numbers k such that the least prime dividing the sum of divisors of k is equal to the least prime not dividing k.

Original entry on oeis.org

8, 15, 21, 27, 32, 33, 35, 39, 45, 50, 51, 55, 57, 63, 65, 69, 75, 77, 85, 87, 91, 93, 95, 98, 99, 105, 111, 115, 117, 119, 123, 125, 128, 129, 133, 135, 141, 143, 145, 147, 153, 155, 159, 161, 165, 171, 175, 177, 183, 185, 187, 189, 195, 196, 200, 201, 203, 205, 207, 209, 213, 215, 217, 219, 221, 231, 235, 237

Offset: 1

Antti Karttunen, Aug 06 2024

nonn

Intersection of A002808 and A374475.
Cf. A000203, A020639, A053669, A374474.
Cf. A228058 (subsequence), and also A324534, A351458, A364286.

isA374476(n) = (!isprime(n) && A374474(n));

cp's OEIS Frontend

A324644 a(n) = gcd(sigma(n), A276086(n)).

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