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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 (list; graph; refs; listen; history; text; internal format)
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: A303812 A259028 A317392 * A219258 A044861 A161835

Adjacent sequences:  A234637 A234638 A234639 * A234641 A234642 A234643

KEYWORD

nonn

AUTHOR

M. F. Hasler, Dec 28 2013

STATUS

approved

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Last modified June 24 10:10 EDT 2019. Contains 324323 sequences. (Running on oeis4.)