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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
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 26 16:32 EST 2021. Contains 341632 sequences. (Running on oeis4.)