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A102788 Integer part of n#/((p-7)# 7#), where p=preceding prime to n. 0

%I

%S 0,0,0,0,1,4,11,19,35,3,4,5,7,310,394,11,14,17,19,22,1653,27,31,35,0,

%T 46,4805,5300,5720,6275,0,79,85,90,0,107,112,121,129,137,147,154,0,

%U 175,34581,36029,1,1,241,55200,57676,265,274,1,307,321,336,347,357,370

%N Integer part of n#/((p-7)# 7#), where p=preceding prime to n.

%C 0# = 1# = 2 by convention.

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

%o (PARI) c(n,r) = { local(p); forprime(p=2,n, print1(floor(primorial(p)/primorial(p-r)/primorial(r)+.0)",") ) } 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) }

%K easy,nonn

%O 2,6

%A _Cino Hilliard_, Feb 25 2005

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Last modified July 10 11:42 EDT 2020. Contains 335576 sequences. (Running on oeis4.)