A348276 Numbers k such that k and k+1 are both noninfinitary abundant numbers (A348274).

64198575, 84909824, 86424975, 110238975, 113223824, 191206575, 211266224, 224722575, 231058575, 231800624, 240069375, 240584175, 245383424, 262648575, 262911824, 279597824, 293893424, 297774224, 333773055, 338676975, 340250624, 340829775, 347244975, 372683024

Offset

1,1

Links

Table of n, a(n) for n=1..24.

Example

64198575 is a term since A348271(64198575) = 69470136 > 64198575 and A348271(64198576) = 65363424 > 64198576.

Mathematica

f[p_, e_] := Module[{b = IntegerDigits[e, 2], m}, m = Length[b]; Product[If[b[[j]] > 0, 1 + p^(2^(m - j)), 1], {j, 1, m}]]; isigma[1] = 1; isigma[n_] := Times @@ f @@@ FactorInteger[n]; q[n_] := DivisorSigma[1, n] - isigma[n] > n; seq = {}; q1 = q[1]; Do[q2 = q[n]; If[q1 && q2, AppendTo[seq, n-1]]; q1=q2 , {n, 2, 10^8}]; seq

Crossrefs

Cf. A348271.

Subsequence of A096399 and A348274.

Similar sequences: A318167, A327635, A327942, A331412.

Sequence in context: A223288 A223485 A250863 * A164725 A164726 A237157

Adjacent sequences: A348273 A348274 A348275 * A348277 A348278 A348279

Keyword

nonn

Author

Amiram Eldar, Oct 09 2021

Status

approved