A306985 Numbers k such that isigma(k) = isigma(k+1), where isigma(k) is the sum of the infinitary divisors of k (A049417).

14, 27, 44, 459, 620, 957, 1334, 1634, 1652, 2204, 2685, 3195, 3451, 3956, 4064, 4544, 5547, 8495, 8636, 8907, 9844, 11515, 15296, 19491, 20145, 20155, 27643, 31724, 33998, 38180, 41265, 41547, 42818, 45716, 48364, 61964, 64665, 74875, 74918, 79316, 79826

Offset: 1

Author

Amiram Eldar, Mar 18 2019

Keywords

• nonn

Comments

a(n) differs from A293183(n) starting at n = 15.

Examples

			14 is in the sequence since isigma(14) = isigma(15) = 24.
		

Links

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

Crossrefs

Cf. A002961, A049417, A064125, A293183.

Programs

Mathematica

fun[p_,e_] := Module[{ b = IntegerDigits[e,2]}, m=Length[b]; Product[If[b[[j]]>0, 1+p^(2^(m-j)),1], {j,1,m}]]; isigma[1]=1; isigma[n_] := Times @@ fun @@@ FactorInteger[n]; aQ[n_] := isigma[n] == isigma[n+1]; Select[Range[1000], aQ]