|
|
A060238
|
|
a(n) = det(M) where M is an n X n matrix with M[i,j] = lcm(i,j).
|
|
7
|
|
|
1, 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
|
0,3
|
|
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
|
|
|
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_{p<=n} (1-p)^floor(n/p) where the product runs through the primes. - Benoit Cloitre, Jan 31 2008
|
|
MAPLE
|
|
|
MATHEMATICA
|
|
|
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
|
|
|
KEYWORD
|
sign
|
|
AUTHOR
|
MCKAY john (mckay(AT)cs.concordia.ca), Mar 21 2001
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|