A179859 Numbers k that divide the sum of the first k noncomposites.

1, 3, 7, 225, 487, 735, 50047, 142835, 170209, 249655, 316585343, 374788043, 2460457827, 2803329305, 6860334657, 65397031525, 78658228039

Offset

1,2

Comments

A variant of A045345 (primes), A053781 (composites) and A129749 (nonprimes).

Links

Table of n, a(n) for n=1..17.

Formula

Numbers k such that k | A014284(k).

a(n) = A179861(n) / A179860(n).

a(n+1) = A158682(n) + 1.

Example

The sum of the first 7 noncomposites is 42 = 6*7, so 7 is in the sequence.

Prog

(PARI) lista(kmax) = {my(m = 1, s = 1); print1(1, ", "); forprime(k = 1, kmax, m++; s += k; if(!(s % m), print1(m, ", "))); } \\ Amiram Eldar, May 24 2024

Crossrefs

Cf. A008578 (noncomposites), A014284 (sum of first n noncomposites).

Cf. A045345, A053781, A129749, A179860, A179861.

Sequence in context: A057619 A349006 A349838 * A061422 A206333 A088097

Adjacent sequences: A179856 A179857 A179858 * A179860 A179861 A179862

Keyword

nonn,more

Author

Ray Chandler, Jul 29 2010

Extensions

a(16)-a(17) from Amiram Eldar, May 24 2024

Status

approved