A102790 Integer part of n#/(p-3)#, where p=preceding prime to n.

3, 15, 35, 11, 143, 17, 323, 23, 29, 899, 37, 41, 1763, 47, 53, 59, 3599, 67, 71, 5183, 79, 83, 89, 97, 101, 10403, 107, 11663, 113, 127, 131, 137, 19043, 149, 22499, 157, 163, 167, 173, 179, 32399, 191, 36863, 197, 39203, 211, 223, 227, 51983, 233, 239, 57599

Offset

2,1

Comments

0# = 1# = 2 by convention.

Links

Table of n, a(n) for n=2..53.

Formula

n# = product of primes <= n. 0#=1#=2. n#/(p-r)# is analogous to the number of permutations of n things taken r at a time: P(n, r) = n!/(n-r)! where factorial ! is replaced by primorial # and n is replaced with the preceding prime to n.

Prog

(PARI) perm(n, r) = { local(p); forprime(p=r, n, print1(floor(primorial(p)/primorial(p-r))", ") ) } primorial(n) = \ The product of primes <= n using the pari primelimit. { local(p1, x); if(n==0||n==1, return(2)); p1=1; forprime(x=2, n, p1*=x); return(p1) }

Crossrefs

Sequence in context: A324303 A009261 A331249 * A317182 A236693 A317183

Adjacent sequences: A102787 A102788 A102789 * A102791 A102792 A102793

Keyword

easy,nonn

Author

Cino Hilliard, Feb 25 2005

Status

approved