cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

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

Original entry on oeis.org

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

Views

Author

Ray Chandler, Jul 29 2010

Keywords

Comments

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

Examples

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

Crossrefs

Cf. A008578 (noncomposites), A014284 (sum of first n noncomposites).
Cf. A045345, A053781, A129749, A179860, A179861.

Programs

  • 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

Formula

Numbers k such that k | A014284(k).
a(n) = A179861(n) / A179860(n).
a(n+1) = A158682(n) + 1.

Extensions

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

A179860 Integer averages of first n noncomposites for some n.

Original entry on oeis.org

1, 2, 6, 636, 1592, 2574, 292656, 917042, 1108972, 1678508, 3334890730, 3981285760, 28567166356, 32739591796, 83332116034, 871263881618, 1055495274756
Offset: 1

Views

Author

Ray Chandler, Jul 29 2010

Keywords

Comments

A variant of A050248 (primes), A073263 (composites) and A160758 (nonprimes).

Examples

			Sum of first 7 noncomposites is 42; 42 / 7 = 6 is in the sequence.

Crossrefs

Cf. A008578 (noncomposites), A014284 (sum of first n noncomposites).
Cf. A179859, A179861, A158682.

Formula

a(n) = A179861(n) / A179859(n) = A014284(A179859(n)) / A179859(n).

Extensions

a(16)-a(17) from Robert Price, Apr 21 2013
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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