A384840 Numbers k for which sigma(k - x) + sigma(k + x) = 7*k has at least one nonnegative solution.

1952, 1992, 2016, 2160, 2520, 2640, 3314, 3744, 3801, 4320, 4484, 4500, 4566, 4620, 4680, 4994, 5016, 5948, 6072, 6096, 6194, 6384, 6492, 6552, 6654, 6870, 7056, 7200, 7224, 7382, 7435, 7440, 7470, 7794, 7812, 7920, 7956, 8376, 8480, 8604, 8616, 8702, 8892, 9284, 9360, 9408

Offset: 1

Author

Michel Marcus, Jun 10 2025

Keywords

• nonn

Links

• Michel Marcus, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000203 (sigma), A055153 (a subsequence).

Cf. A383268, A384838, A384839, A384841.

Cf. A383758.

Programs

PARI

isok(k) = for (x=0, k-1, if (sigma(k - x) + sigma(k + x) == 7*k, return(1)));