A330579 -id:A330579 - cp's OEIS frontend

A330578 a(n) is the remainder when the sum of the first n composite numbers is divided by the n-th composite number.

0, 4, 2, 0, 7, 1, 7, 3, 14, 4, 12, 6, 21, 7, 24, 16, 7, 25, 5, 15, 4, 26, 14, 1, 11, 36, 22, 34, 4, 33, 17, 31, 14, 46, 28, 9, 23, 3, 38, 17, 53, 9, 25, 2, 42, 18, 59, 9, 52, 26, 44, 64, 37, 9, 57, 28, 48, 18, 69, 7, 60, 28, 82, 49, 71, 37, 2, 59, 23, 81, 44

Offset: 1

Rémy Sigrist, Dec 18 2019

nonn

			a(3) = (4 + 6 + 8) mod 8 = 2.

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Cf. A002808, A053767, A071089 (prime variant), A330579 (positions of zeros).

s=0; forcomposite (c=4, 96, s+=c; print1 (s%c", "))

a(n) = A053767(n) mod A002808(n).

A330580 Composite numbers n that divide the sum of all composite numbers <= n.

Original entry on oeis.org

4, 9, 604, 1849, 7123, 29588, 71056, 317238, 945414, 1347895, 3567705, 4624025, 8518502, 1523051853, 4353560959, 7537630621, 24916885136, 41483524658, 513849020166, 1021228997529, 1137756574012, 1185967711155, 1581191501535, 1705826324526

Offset: 1

Rémy Sigrist, Dec 18 2019

Cf. A002808, A007506 (prime variant), A330579.

s=0; k=0; forcomposite (c=4, oo, k++; s+=c; if (s%c==0, print1 (c", ")))

a(n) = A002808(A330579(n)).

a(15)-a(24) from Giovanni Resta, Dec 20 2019

cp's OEIS Frontend

A330578 a(n) is the remainder when the sum of the first n composite numbers is divided by the n-th composite number.

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