A324310 Numbers k such that s(k) = s(k+1) = s(k+2) where s(k) is the sum of divisors of k that are smaller than sqrt(k) (A070039).

2, 3, 2505, 64486, 113413, 205365, 423414, 496156, 635053, 664033, 881565, 1011793, 1190685, 1306605, 1442136, 1923655, 1947766, 2286913, 2324422, 2465805, 3030733, 3291553, 3335205, 4100086, 4547353, 4648965, 4987065, 5025705, 5034904, 5069113, 5827485, 5909413

Offset

1,1

Comments

Are there 4 consecutive numbers with the same value of A070039, apart from 2, 3, 4, 5?

The next 4 consecutive numbers with the same value of A070039 start at 1190499411. - Giovanni Resta, Sep 05 2019

Links

Table of n, a(n) for n=1..32.

Example

2 is in the sequence since A070039(2) = A070039(3) = A070039(4) = 1.

Mathematica

s[n_] := DivisorSum[n, # &, # < Sqrt[n] &]; seq={}; s1 = 0; s2=0; Do[s3 = s[n]; If[s1 == s2 && s2 == s3, AppendTo[seq, n - 2]]; s1 = s2; s2 = s3, {n, 2, 10^5}]; seq

Crossrefs

Cf. A070039, A324295, A325175.

Sequence in context: A288171 A137321 A066848 * A125612 A185156 A235935

Adjacent sequences: A324307 A324308 A324309 * A324311 A324312 A324313

Keyword

nonn

Author

Amiram Eldar, Sep 03 2019

Status

approved