A176555 Noncomposite concatenations of divisors of some k, ordered by k.

1, 13, 17, 139, 113, 13721, 131, 137, 167, 173, 179, 197, 1103, 1109, 111121, 1151, 1163, 1181, 1361183, 1193, 1373219, 1223, 1229, 1379237, 1277, 1283, 1307, 131133121363, 1367, 1373, 13127381, 1409, 1433, 1439, 13157471, 1487, 13163489, 1499, 1773511, 1523, 1571, 1601

Offset

1,2

Comments

Intersection of A037278 and A018252.

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Formula

a(n) = A037278(A176553(n)).

Example

For n = 6; a(6) = 13721 because A176553(6) = 21, and divisors of 21 are 1, 3, 7, 21; concatenation of divisors A037278(21) = 13721 is noncomposite number.

Mathematica

Select[Map[FromDigits[Flatten[IntegerDigits[Divisors[#]]]] &, Range[1000]], !CompositeQ[#] &] (* Paolo Xausa, Nov 06 2025 *)

Crossrefs

Cf. A176553, A018252, A037278.

Sequence in context: A210547 A202136 A123909 * A237423 A342725 A292003

Adjacent sequences: A176552 A176553 A176554 * A176556 A176557 A176558

Keyword

nonn,base

Author

Jaroslav Krizek, Apr 20 2010

Extensions

Extended and edited by Charles R Greathouse IV, Apr 27 2010

More terms from Paolo Xausa, Nov 06 2025

Status

approved