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A234640
Odd numbers n for which sigma(sigma(sigma(n))) is odd.
1
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.
PROG
(PARI) forstep(n=1, 1999, 2, sigma(sigma(sigma(n)))%2 && print1(n", "))
CROSSREFS
Sequence in context: A358425 A317392 A373505 * A219258 A044861 A161835
KEYWORD
nonn
AUTHOR
M. F. Hasler, Dec 28 2013
STATUS
approved