A171439 Doubly Orderly Numbers: composite numbers that are orderly for two values of k.

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.

Links

Table of n, a(n) for n=1..23.

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

Adjacent sequences: A171436 A171437 A171438 * A171440 A171441 A171442

Keyword

nonn

Author

Andrew Weimholt, Dec 09 2009

Status

approved