A324295 Numbers k such that s(k) = s(k+1) where s(k) is the sum of divisors of k that are smaller than sqrt(k) (A070039).

2, 3, 4, 186, 318, 434, 473, 582, 730, 978, 1024, 1035, 1245, 1357, 1397, 1506, 1661, 1902, 2085, 2116, 2224, 2329, 2453, 2505, 2506, 2770, 2954, 3144, 3345, 3377, 3624, 3641, 3765, 3790, 3882, 4037, 4172, 4438, 4898, 4938, 4975, 5221, 6126, 6285, 6312, 6356

Offset

1,1

Links

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

Example

186 is in the sequence since A070039(186) = A070039(187) = 12.

Mathematica

s[n_] := DivisorSum[n, # &, # < Sqrt[n] &]; seq={}; s1 = 0; Do[s2 = s[n]; If[s1 == s2, AppendTo[seq, n - 1]]; s1 = s2, {n, 2, 6500}]; seq

Crossrefs

Cf. A002961, A064115, A064125, A070039, A164522, A164557, A293183, A306985, A325175.

Sequence in context: A127280 A229622 A244552 * A037433 A085933 A244547

Adjacent sequences: A324292 A324293 A324294 * A324296 A324297 A324298

Keyword

nonn

Author

Amiram Eldar, Sep 03 2019

Status

approved