|
Search: id:A102791
|
|
|
| A102791 |
|
Integer part of n#/(p-5)#, where p=preceding prime to n. |
|
+0
1
|
|
| 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
(list; graph; listen)
|
|
|
OFFSET
|
5,1
|
|
|
COMMENT
|
0# = 1# = 2 by convention.
|
|
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.
|
|
PROGRAM
|
(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: A111370 A093739 A085465 this_sequence A061550 A090454 A047640
Adjacent sequences: A102788 A102789 A102790 this_sequence A102792 A102793 A102794
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Cino Hilliard (hillcino368(AT)gmail.com), Feb 25 2005
|
|
|
Search completed in 0.002 seconds
|
