A333949 Numbers k such that s(k) = s(k+1), where s(k) is the sum of recursive divisors of k (A333926).

14, 206, 957, 1334, 1364, 1485, 1634, 2685, 2974, 4136, 4364, 14841, 20145, 24957, 33998, 36566, 42818, 64672, 74918, 79826, 79833, 84134, 86343, 92685, 109864, 111506, 122073, 138237, 147454, 159711, 162602, 166934, 187863, 190773, 193893, 201597, 274533, 288765

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Example

14 is a term since A333926(14) = A333926(15) = 24.

Mathematica

recDivQ[n_, 1] = True; recDivQ[n_, d_] := recDivQ[n, d] = Divisible[n, d] && AllTrue[FactorInteger[d], recDivQ[IntegerExponent[n, First[#]], Last[#]] &]; recDivs[n_] := Select[Divisors[n], recDivQ[n, #] &]; f[p_, e_] := 1 + Total[p^recDivs[e]]; recDivSum[1] = 1; recDivSum[n_] := Times @@ (f @@@ FactorInteger[n]); Select[Range[10^5], recDivSum[#] == recDivSum[# + 1] &]

Crossrefs

Cf. A333926.

Analogous sequences: A002961, A064115 (nonunitary), A064125 (unitary), A293183 (bi-unitary), A306985 (infinitary).

Sequence in context: A113349 A109764 A349283 * A002961 A063071 A251963

Adjacent sequences: A333946 A333947 A333948 * A333950 A333951 A333952

Keyword

nonn

Author

Amiram Eldar, Apr 11 2020

Status

approved