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A171439
Doubly Orderly Numbers: composite numbers that are orderly for two values of k.
0
393625, 1106861, 2480233, 3166919, 5919509, 6099895, 6440375, 6600349, 8660407, 11407151, 12780523, 14753065, 16900639, 18821573, 21707441, 22671125, 23080813, 23165125, 24924335, 27200929, 28514195, 29947673, 30452005
OFFSET
1,1
COMMENTS
See A167408 for the definition of Orderly.
All doubly orderly numbers are orderly modulo k=tau(n)+1 and k=tau(n)+3, and are also "very orderly" (Cf. A167409).
Composite numbers appearing in both A167409 and A168003.
No composite number is orderly for more than two values of k, and 11 is the only prime which is orderly for exactly two values of k. 11 does not appear in this sequence as the definition of "doubly orderly" applies only to composite numbers.
EXAMPLE
393625 is in the list because it is orderly modulo 17 and 19
.{1,1175,15745,3149,5,125,393625,25,1675,5875,8375,335,47,235,78725,67} == {1,2,3,...,16} mod 17
.{1,393625,1675,5875,5,25,235,78725,47,67,125,335,15745,3149,8375,1175} == {1,2,3,...,16} mod 19
CROSSREFS
Cf. A167408 - Orderly Numbers
Cf. A167409 - Very Orderly Numbers
Cf. A168003 - Numbers which are orderly modulo tau(n)+3
Sequence in context: A157623 A145228 A204628 * A210162 A320209 A320218
KEYWORD
nonn
AUTHOR
Andrew Weimholt, Dec 09 2009
STATUS
approved