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.

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A385209 Least k such that A086369(k) = n.

Original entry on oeis.org

1, 2, 3, 4, 9, 6, 15, 16, 81, 12, 45, 64, 729, 24, 105, 36, 225, 48, 405, 1024, 59049, 60, 315, 4096, 531441, 192, 3645, 144, 2025, 120, 945, 65536, 43046721, 180, 1575, 262144, 387420489, 240, 2835, 576, 18225, 3072, 295245, 4194304, 31381059609, 360, 3465, 1296
Offset: 1

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Author

Miles Englezou, Jun 21 2025

Keywords

Comments

A086369(n) is also the cardinality of the set containing the divisors d of n and those 0 < m < n satisfying m + d = n.

Examples

			a(4) = 4 since 4 is the least k such that A086369(k) = 4.
a(13) = 729 since 729 is the least k such that A086369(k) = 13.

Crossrefs

Cf. A086369, A385202.

Programs

  • PARI
    a(n,k) = my(f); (f(n) = if(n%2==1, 1+2*sumdiv(n,d,d

Formula

a(2*p-1) = 3^(p-1) for prime p. - Jinyuan Wang, Jun 30 2025

Extensions

a(45)-a(48) from Jinyuan Wang, Jun 30 2025
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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