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A014597
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Numbers n such that n^2 is a sum of distinct factorials.
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7
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1, 3, 5, 11, 12, 27, 29, 71, 72, 213, 215, 603, 635, 1917, 1183893
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| If there are any terms in either A014597 or A025494 beyond the last one given (i.e. n = 1183893 in A014597; equivalently n^2 = 1401602635449 in A025494), then n^2 must be greater than 48! (about 1.24139e+61). - Jon Schoenfield, Aug 04 2006
A197183(a(n)) = 1. [Reinhard Zumkeller, Dec 04 2011]
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REFERENCES
| Posting by Dan Hoey (Hoey(AT)aic.nrl.navy.mil) to math-fun mailing list.
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LINKS
| Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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EXAMPLE
| 1183893^2 = 1!+2!+3!+7!+8!+9!+10!+11!+12!+13!+14!+15!
2 is not a member since 4 is not a sum of distinct factorials.
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PROG
| (Haskell)
import Data.List (elemIndices)
a014597 n = a014597_list !! (n-1)
a014597_list = tail $ elemIndices 1 $ map a197183 [0..]
-- Reinhard Zumkeller, Dec 04 2011
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CROSSREFS
| Cf. A025494, A059589, A051761.
Sequence in context: A066281 A072063 A115398 * A130603 A069977 A065396
Adjacent sequences: A014594 A014595 A014596 * A014598 A014599 A014600
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KEYWORD
| nonn,more,nice
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AUTHOR
| Eric Weisstein (eric(AT)weisstein.com)
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EXTENSIONS
| 15th term from Jud McCranie (JudMcCranie(AT)ugaalum.uga.edu), who remarks that there no others involving terms < 21!.
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