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 A060238 det(M) where M is an n X n matrix with M[i,j] = lcm(i,j). 6
 1, -2, 12, -48, 960, 11520, -483840, 3870720, -69672960, -2786918400, 306561024000, 7357464576000, -1147764473856000, -96412215803904000, -11569465896468480000, 185111454343495680000, -50350315581430824960000, -1812611360931509698560000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES J.-M. De Koninck & A. Mercier, 1001 Problèmes en Théorie Classique des Nombres, Problème 695, pp. 90, 297-298, Ellipses, Paris, 2004. J. Sandor and B. Crstici, Handbook of Number Theory II, Springer, 2004, p. 265, eq. 10. LINKS Enrique Pérez Herrero, Table of n, a(n) for n = 1..200 FORMULA For n >= 2, a(n) = n! * Product_{j=2..n} Product_{p|j} (1-p) (where the second product is over all primes p that divide j) (cf. A023900). - Avi Peretz (njk(AT)netvision.net.il), Mar 22 2001 a(n) = n! * Product_{pn!*mul((1-ithprime(i))^floor(n/ithprime(i)), i=1..numtheory[pi](n)): seq(A060238(n), n=1..20); # Wesley Ivan Hurt, Aug 15 2016 MATHEMATICA A060238[n_]:=n!*Product[(1 - Prime[i])^Floor[n/Prime[i]], {i, PrimePi[n]}]; Array[A060238, 20] (* Enrique Pérez Herrero, Jun 08 2010 *) PROG (PARI) a(n)=n!*prod(p=1, sqrtint(n), if(isprime(p), (1-p)^floor(n/p), 1)) \\ Benoit Cloitre, Jan 31 2008 CROSSREFS Cf. A000142, A001088, A013939, A023900, A048803, A060239, A085542. Sequence in context: A277183 A052588 A139239 * A085495 A119978 A139234 Adjacent sequences:  A060235 A060236 A060237 * A060239 A060240 A060241 KEYWORD sign AUTHOR MCKAY john (mckay(AT)cs.concordia.ca), Mar 21 2001 STATUS approved

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Last modified April 14 12:11 EDT 2021. Contains 342949 sequences. (Running on oeis4.)