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A001088 Product of totient function: a(n) = Product_{k=1..n} phi(k) (cf. A000010). 21
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; text; internal format)
OFFSET

1,3

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

The matrix M(i,j) = gcd(i,j) is sequence A003989. - Michael Somos, Jun 25 2012

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.

M. Petkovsek et al., A=B, Peters, 1996, p. 21.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..100

Antal Bege, Hadamard product of GCD matrices, Acta Univ. Sapientiae, Mathematica, 1, 1 (2009) 43-49.

Warren P. Johnson, An LDU Factorization in Elementary Number Theory, Mathematics Magazine, 76 (2003), 392-394.

P. Mansion, On an Arithmetical Theorem of Professor Smith's, Messenger of Mathematics, (1878), pp. 81-82.

H. J. S. Smith, On the value of a certain arithmetical determinant, Proc. London Math. Soc. 7 (1875-1876), pp. 208-212.

Eric Weisstein's World of Mathematics, Le Paige's Theorem

Index to divisibility sequences

FORMULA

a(n) = phi(1) * phi(2) * ... * phi(n).

EXAMPLE

a(2) = 1 because the matrix M is: [1,1; 1,2] and det(A) = 1.

MAPLE

with(numtheory, phi); A001088 := proc(n) local i; mul(phi(i), i=1..n); end;

MATHEMATICA

A001088[n_]:=Times@@EulerPhi/@Range[n]; Table[A001088[n], {n, 30}] (* Enrique Pérez Herrero, Sep 19 2010 *)

Rest[FoldList[Times, 1, EulerPhi[Range[30]]]] (* Harvey P. Dale, Dec 09 2011 *)

PROG

(Haskell)

a001088 n = a001088_list !! (n-1)

a001088_list = scanl1 (*) a000010_list

-- Reinhard Zumkeller, Mar 04 2012

(PARI) a(n)=prod(k=1, n, eulerphi(k)) \\ Charles R Greathouse IV, Mar 04 2012

CROSSREFS

Cf. A000010, A060238, A060239, A059381, A059382, A059383, A059384, A002088.

Cf. A003989.

Sequence in context: A081411 A094384 A053038 * A101926 A087965 A074411

Adjacent sequences:  A001085 A001086 A001087 * A001089 A001090 A001091

KEYWORD

nonn,nice,easy

AUTHOR

Simon Plouffe

EXTENSIONS

Catalan reference from Philippe Deléham, Dec 22 2003

STATUS

approved

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Last modified December 21 09:07 EST 2014. Contains 252300 sequences.