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A001088
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Product of totient function: a(n) = Product_{k=1..n} phi(k) (cf. A000010).
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14
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1, 1, 2, 4, 16, 32, 192, 768, 4608, 18432, 184320, 737280, 8847360, 53084160, 424673280, 3397386240, 54358179840, 326149079040, 5870683422720, 46965467381760, 563585608581120, 5635856085811200, 123988833887846400, 991910671102771200, 19838213422055424000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| a(n) is also the determinant of the symmetric n X n matrix M defined by M(i,j) = gcd(i,j) for 1 <= i,j <= n [Smith and Mansion]. - Avi Peretz (njk(AT)netvision.net.il), Mar 20 2001
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REFERENCES
| E. C. Catalan, Theoreme de MM. Smith et Mansion, Nouvelle correspondance mathematique, 4 (1878) 103-112.
D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, Vol. 2, p. 598.
Warren P. Johnson, An LDU Factorization in Elementary Number Theory, Mathematics Magazine, 76 (2003), 392-394.
M. Petkovsek et al., A=B, Peters, 1996, p. 21.
Antal Bege, Hadamard product of GCD matrices, Acta Univ. Sapientiae, Mathematica, 1, 1 (2009) 43-49
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LINKS
| T. D. Noe, Table of n, a(n) for n = 1..100
Eric Weisstein's World of Mathematics, Le Paige's Theorem
Index to divisibility sequences
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FORMULA
| a(n) = phi(1) * phi(2) * ... * phi(n).
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EXAMPLE
| a(2) = 1 because the matrix M is: [1,1; 1,2] and det(A) = 1
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MAPLE
| with(numtheory, phi); A001088 := proc(n) local i; mul(phi(i), i=1..n); end;
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MATHEMATICA
| A001088[n_]:=Times@@EulerPhi/@Range[n]; Table[A001088[n], {n, 30}] (* from Enrique Pérez Herrero, psychgeometry(AT)gmail.com, Sep 19 2010 *)
Rest[FoldList[Times, 1, EulerPhi[Range[30]]]] (* From Harvey P. Dale, Dec 09 2011 *)
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CROSSREFS
| Cf. A000010, A060238, A060239, A059381, A059382, A059383, A059384, A002088.
Sequence in context: A081411 A094384 A053038 * A101926 A087965 A074411
Adjacent sequences: A001085 A001086 A001087 * A001089 A001090 A001091
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KEYWORD
| nonn,nice,easy
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AUTHOR
| Simon Plouffe (simon.plouffe(AT)gmail.com)
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EXTENSIONS
| Catalan reference from DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Dec 22 2003
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