A115649 Numbers whose square is the sum of distinct double factorials (A006882).

1, 2, 3, 4, 5, 7, 8, 11, 13, 20, 21, 31, 38, 62, 63, 65, 66, 70, 72, 102, 107, 109, 120, 125, 217, 218, 238, 240, 373, 382, 387, 427, 439, 834, 840, 890, 915, 1440, 1474, 1638, 1650, 3213, 3220, 3241, 3332, 3540, 5886, 6751, 6855, 13730, 14078, 14911

Offset: 1

Author

Giovanni Resta, Jan 28 2006

Keywords

• nonn

Comments

Double factorials 0!! and 1!! are not considered distinct. Note that double factorial (n!!) is different from (n!)!.

Examples

			102^2 = 1!! + 4!! + 11!!.
		

Crossrefs

Cf. A006882, A115648, A115650.