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

1,2

Comments

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

Links

Table of n, a(n) for n=1..52.

Example

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

Crossrefs

Cf. A006882, A115648, A115650.

Sequence in context: A118083 A241093 A116470 * A191168 A309879 A191166

Adjacent sequences: A115646 A115647 A115648 * A115650 A115651 A115652

Keyword

nonn

Author

Giovanni Resta, Jan 28 2006

Status

approved