A280636 Semiprime numbers whose digit string can be partitioned into three parts such that the product of the first two parts equals the third part.

111, 122, 133, 155, 166, 177, 326, 339, 515, 717, 818, 2918, 3721, 5315, 6742, 7214, 7642, 9327, 9763, 11111, 11333, 11555, 12929, 13333, 13535, 13565, 13791, 13939, 14114, 14141, 14242, 14545, 15115, 15151, 15353, 15454, 15757, 16161, 16565

Offset

1,1

Comments

Could be called semiprime area numbers. If the first set of digits of the number is considered the length, the second set of digits of the number is considered the width, and the final set of digits of the number is considered the area, then length * width = area.

Links

Table of n, a(n) for n=1..39.

Formula

A001358 INTERSECT A280635.

Example

2918 is semiprime (2*1459) and an area number (2*9 = 18).
6742 is semiprime (2*3371) and an area number (6*7 = 42).
Leading zeros are not allowed.

Crossrefs

Cf. A088294, A280635.

Sequence in context: A343760 A280635 A280732 * A034840 A135643 A070798

Adjacent sequences: A280633 A280634 A280635 * A280637 A280638 A280639

Keyword

nonn,base

Author

Randy L. Ekl, Jan 06 2017

Status

approved