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A115654 Semiprimes (A001358) which are the sum of distinct double factorials (A006882). 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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..56.

EXAMPLE

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

MATHEMATICA

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

CROSSREFS

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

Sequence in context: A253106 A320969 A113433 * A036326 A078972 A115652

Adjacent sequences:  A115651 A115652 A115653 * A115655 A115656 A115657

KEYWORD

nonn

AUTHOR

Giovanni Resta, Jan 28 2006

STATUS

approved

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Last modified February 25 08:33 EST 2021. Contains 341606 sequences. (Running on oeis4.)