A334020 Numbers k such that s(k) = s(k+1), where s(k) is the sum of unitary divisors of k that are smaller than sqrt(k) (A334019).

2, 3, 4, 7, 8, 16, 31, 127, 186, 256, 318, 434, 473, 574, 582, 588, 730, 735, 819, 978, 1245, 1357, 1374, 1397, 1420, 1421, 1500, 1506, 1661, 1694, 1902, 1956, 1988, 2059, 2085, 2147, 2166, 2329, 2453, 2505, 2506, 2534, 2754, 2770, 2868, 2954, 2988, 3345, 3377

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

2 is a term since A334019(2) = A334019(3) = 1.

Mathematica

s[n_] := DivisorSum[n, # &, #^2 < n && CoprimeQ[#, n/#] &]; Select[Range[3000], s[#] == s[# + 1] &]

Crossrefs

Cf. A064125, A324295, A334019,

Sequence in context: A333801 A239973 A281782 * A006549 A134459 A225211

Adjacent sequences: A334017 A334018 A334019 * A334021 A334022 A334023

Keyword

nonn

Author

Amiram Eldar, Apr 12 2020

Status

approved