A348628 Numbers k such that k and k+1 have the same sum of nonexponential divisors (A160135).

1, 2, 3, 4, 15, 44, 674, 478899

Offset

1,2

Comments

Numbers k such that A160135(k) = A160135(k+1).

a(9) > 1.6 * 10^11, if it exists.

Links

Table of n, a(n) for n=1..8.

Example

2 is a term since A160135(2) = A160135(3) = 1.
15 is a term since A160135(15) = A160135(16) = 9.

Mathematica

esigma[n_] := Times @@ (Sum[First[#]^d, {d, Divisors[Last[#]]}] &) /@ FactorInteger[n]; s[1] = 1; s[n_] := DivisorSigma[1, n] - esigma[n]; Select[Range[500000], s[#] == s[# + 1] &]

Crossrefs

Cf. A160135.

Similar sequences: A002961, A064115, A064125, A293183, A306985, A348346.

Sequence in context: A295757 A005645 A362639 * A281586 A365739 A217714

Adjacent sequences: A348625 A348626 A348627 * A348629 A348630 A348631

Keyword

nonn,more

Author

Amiram Eldar, Oct 26 2021

Status

approved