A115644 - OEIS

A115644

Brilliant numbers (A078972) that are sums of distinct factorials.

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

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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