A115654 Semiprimes (A001358) which are the sum of distinct double factorials (A006882).

4, 6, 9, 10, 14, 15, 21, 25, 26, 49, 51, 57, 58, 62, 65, 69, 74, 77, 106, 111, 115, 118, 119, 121, 122, 123, 129, 133, 134, 155, 158, 159, 161, 166, 169, 177, 178, 386, 393, 394, 395, 398, 403, 407, 411, 413, 437, 445, 446, 447, 451, 453, 458, 489, 493, 497

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

			384 = 2*19 = 8!!+2!!.
		

Crossrefs

Cf. A006882, A001358, A115651, A115652, A115653.

Programs

Mathematica

Union[Select[Total/@Subsets[Range[10]!!,10],PrimeOmega[#]==2&]] (* Harvey P. Dale, Aug 24 2012 *)