A384839 Numbers k for which sigma(k - x) + sigma(k + x) = 6*k has at least one nonnegative solution.

93, 120, 204, 211, 231, 239, 254, 269, 274, 280, 315, 336, 343, 360, 366, 372, 375, 378, 395, 396, 402, 420, 466, 475, 496, 592, 604, 672, 708, 724, 726, 774, 821, 822, 827, 836, 840, 844, 845, 862, 870, 880, 898, 919, 926, 952, 964, 976, 982, 996, 997, 1023, 1077, 1080

Offset: 1

Author

Michel Marcus, Jun 10 2025

Keywords

• nonn

Links

• Michel Marcus, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A000203 (sigma), A005820 (a subsequence).

Cf. A383268, A384838, A384840, A384841.

Cf. A383758.

Programs

Mathematica

s={};Do[Do[If[DivisorSigma[1,k-x]+DivisorSigma[1,k+x]==6*k,AppendTo[s,k];Break[]],{x,0,k-1}],{k,1,1080}];s (* James C. McMahon, Jun 20 2025 *)

PARI

isok(k) = for (x=0, k-1, if (sigma(k - x) + sigma(k + x) == 6*k, return(1)));