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Search: id:A055486
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| A055486 |
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Number of solutions to Sigma[x] = n!. |
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+0
4
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| 1, 0, 1, 3, 4, 15, 33, 111, 382, 1195, 3366, 14077, 53265, 229603, 910254
(list; graph; listen)
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OFFSET
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1,4
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REFERENCES
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R. K. Guy (1981): Unsolved Problems In Number Theory, B39.
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FORMULA
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a(n) = A054973(n!) = Cardinality[{x; A000203(x) = A000142(n)}]
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EXAMPLE
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n = 9, n! = 362880 and the solution set is {97440,...,205634,..,361657} of 382 integers x, so that sigma(x) = 9!, thus a(9) = 382
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MAPLE
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with(numtheory):for f from 1 to 9 do fac := f!: k := 0:for n from 1 to fac do if sigma(n)=fac then k := k+1: fi: od: print( k); od:
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CROSSREFS
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Cf. A000142, A000203, A054973, A014197, A055488, A055489.
Sequence in context: A167367 A024858 A135100 this_sequence A041665 A052133 A127144
Adjacent sequences: A055483 A055484 A055485 this_sequence A055487 A055488 A055489
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KEYWORD
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more,nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jun 28 2000
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EXTENSIONS
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More terms from Jud McCranie (j.mccranie(AT)comcast.net), Oct 09 2000
a(13)-a(14) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Nov 22 2008
a(15) from Ray Chandler (rayjchandler(AT)sbcglobal.net), Jan 13 2009
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