A102791 Integer part of n#/(p-5)#, where p=preceding prime to n.

15, 105, 77, 143, 221, 323, 437, 29, 899, 37, 1517, 1763, 2021, 53, 59, 3599, 67, 4757, 5183, 79, 6557, 89, 97, 9797, 10403, 11021, 11663, 12317, 127, 16637, 137, 19043, 149, 22499, 157, 163, 27221, 173, 179, 32399, 191, 36863, 38021, 39203, 211, 223

Offset

5,1

Comments

0# = 1# = 2 by convention.

Links

Table of n, a(n) for n=5..50.

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: A227331 A223441 A300295 * A335672 A160892 A061550

Adjacent sequences: A102788 A102789 A102790 * A102792 A102793 A102794

Keyword

easy,nonn

Author

Cino Hilliard, Feb 25 2005

Status

approved