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Search: id:A102790
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| A102790 |
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Integer part of n#/(p-3)#, where p=preceding prime to n. |
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+0
1
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| 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
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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0# = 1# = 2 by convention.
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FORMULA
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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.
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PROGRAM
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(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) }
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CROSSREFS
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Sequence in context: A031091 A086380 A009261 this_sequence A000466 A145949 A015809
Adjacent sequences: A102787 A102788 A102789 this_sequence A102791 A102792 A102793
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Feb 25 2005
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