A234640 Odd numbers n for which sigma(sigma(sigma(n))) is odd.

1, 25, 29, 99, 125, 137, 243, 279, 281, 309, 317, 343, 361, 373, 461, 509, 519, 585, 603, 641, 693, 703, 709, 725, 747, 783, 807, 809, 875, 883, 895, 905, 929, 933, 979, 995, 1003, 1007, 1043, 1059, 1091, 1121, 1133, 1323, 1591, 1597, 1701, 1707, 1779, 1801, 1895, 1973

Offset

1,2

Comments

Also, odd numbers such that sigma(sigma(n)) is in A028982.

Subsequence of odd terms of A234639. See also A234638, and A234641 with further cross references.

Links

Table of n, a(n) for n=1..52.

Prog

(PARI) forstep(n=1, 1999, 2, sigma(sigma(sigma(n)))%2 && print1(n", "))

Crossrefs

Sequence in context: A358425 A317392 A373505 * A219258 A044861 A161835

Adjacent sequences: A234637 A234638 A234639 * A234641 A234642 A234643

Keyword

nonn

Author

M. F. Hasler, Dec 28 2013

Status

approved