A233929 Smallest x such that sigma(x) == n-1 (mod n).

1, 1, 7, 2, 3, 2401, 5, 4, 7, 18, 21, 9604, 6, 9, 13, 8, 44, 21609, 10, 18, 19, 289, 36, 9604, 14, 162, 57, 72, 12, 2614689, 29, 16, 21, 625, 63, 38416, 22, 4608, 37, 18, 27, 21609, 20, 289, 43, 36, 50, 38416, 33, 196, 111, 162, 157, 28561, 34, 1296, 28, 49

Offset

1,3

Comments

Right subdiagonal of A074625.

Records values are: 1, 7, 2401, 9604, 21609, 2614689, 21215236, 36324729, 53304601, 338964921, 431642176, 528264256, 1307979556, ... obtained at indices: 1, 3, 6, 12, 18, 30, 60, 210, 288, 384, 534, 630, 732. - Michel Marcus, Dec 22 2013

Links

Michel Marcus and Donovan Johnson, Table of n, a(n) for n = 1..3000 (first 800 terms from Michel Marcus)

Prog

(PARI) a(n) = {x = 1; while ((sigma(x) % n) != (n - 1), x++); x; } \\ Michel Marcus, Dec 18 2013

Crossrefs

Cf. A000203, A070982, A074625.

Sequence in context: A193027 A248288 A248287 * A241427 A197761 A199269

Adjacent sequences: A233926 A233927 A233928 * A233930 A233931 A233932

Keyword

nonn

Author

Michel Marcus, Dec 18 2013

Status

approved