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A115644 Brilliant numbers (A078972) that are sums of distinct factorials. 2
6, 9, 25, 121, 841, 871, 5041, 5767, 363721, 368761, 409111, 3633841, 3992431, 3992551, 4032121, 4037791, 39962281, 39962311, 39963031, 40279711, 40279801, 43585921, 43591687, 43909207, 479047801, 479365321, 479370271, 482631271 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..28.

EXAMPLE

39962281 = 11! + 8! + 7! + 5!+ 1! = 4861*8221.

MATHEMATICA

brillQ[n_] := Block[{d = FactorInteger[n]}, Plus@@Last/@d==2 && (Last/@d=={2} || Length@IntegerDigits@((First/@d)[[1]])==Length@IntegerDigits@((First/@d)[[2]]))]; fac=Range[20]!; lst={}; Do[ n = Plus@@(fac*IntegerDigits[k, 2, 20]); If[brillQ[n], AppendTo[lst, n]], {k, 2^20-1}]; lst

CROSSREFS

Cf. A078972, A025494, A115645, A115646, A089359.

Sequence in context: A093153 A115646 A260565 * A243708 A300345 A024878

Adjacent sequences:  A115641 A115642 A115643 * A115645 A115646 A115647

KEYWORD

nonn

AUTHOR

Giovanni Resta, Jan 27 2006

STATUS

approved

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Last modified July 29 06:21 EDT 2021. Contains 346340 sequences. (Running on oeis4.)