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A115646 Semiprimes (A001358) that are sums of distinct factorials. 2
6, 9, 25, 26, 33, 121, 122, 123, 129, 145, 146, 721, 723, 745, 746, 753, 841, 842, 843, 849, 865, 866, 871, 5041, 5042, 5065, 5071, 5161, 5163, 5169, 5186, 5191, 5761, 5767, 5793, 5905, 5906, 5911, 40321, 40322, 40323, 40345, 40346, 40353, 40441 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Factorials 0! and 1! are not considered distinct.

LINKS

Table of n, a(n) for n=1..45.

EXAMPLE

721 = 6!+1! = 7*103.

MATHEMATICA

semipQ[n_] := Plus @@ Last /@ FactorInteger[n] == 2; fac=Range[10]!; lst={}; Do[ n = Plus@@(fac*IntegerDigits[k, 2, 10]); If[semipQ[n], AppendTo[lst, n]], {k, 2^10-1}]; Union[lst]

CROSSREFS

Cf. A001358, A025494, A115645, A115644, A089359.

Sequence in context: A142877 A260168 A093153 * A260565 A115644 A243708

Adjacent sequences:  A115643 A115644 A115645 * A115647 A115648 A115649

KEYWORD

nonn

AUTHOR

Giovanni Resta, Jan 27 2006

STATUS

approved

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Last modified June 24 08:22 EDT 2017. Contains 288697 sequences.