A327942 Numbers k such that both k and k+1 are nonunitary abundant numbers (A064597).

165375, 893024, 1047375, 1576575, 2282175, 2304224, 2858624, 3614624, 4068224, 4096575, 4597424, 4975424, 6591375, 7574175, 8555624, 9511424, 10446975, 10749375, 10872224, 11477024, 12535424, 13773375, 13946624, 14277375, 15926624, 16041375, 16505775, 16769024

Offset

1,1

Links

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

Example

165375 is in the sequence since both 165375 and 165376 are nonunitary abundant: nusigma(165375) = 179280 > 165375, and nusigma(165376) = 183600 > 165376 (nusigma is the sum of nonunitary divisors, A048146).

Mathematica

f[p_, e_] := (p^(e + 1) - 1)/(p - 1); nuabQ[n_] := Times @@ (f @@@ FactorInteger[n]) - Times @@ (1 + Power @@@ FactorInteger[n]) > n; s = {}; q1 = False; Do[q2 = nuabQ[n]; If[q1 && q2, AppendTo[s, n - 1]]; q1 = q2, {n, 2, 10^7}]; s

Crossrefs

Cf. A048146, A064597, A094889, A307823.

Cf. A096399, A292704, A318167, A327635.

Sequence in context: A233701 A224582 A352974 * A201051 A233425 A183834

Adjacent sequences: A327939 A327940 A327941 * A327943 A327944 A327945

Keyword

nonn

Author

Amiram Eldar, Sep 30 2019

Status

approved