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A102788 Integer part of n#/((p-7)# 7#), where p=preceding prime to n. 0
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, 46, 4805, 5300, 5720, 6275, 0, 79, 85, 90, 0, 107, 112, 121, 129, 137, 147, 154, 0, 175, 34581, 36029, 1, 1, 241, 55200, 57676, 265, 274, 1, 307, 321, 336, 347, 357, 370 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,6

COMMENTS

0# = 1# = 2 by convention.

LINKS

Table of n, a(n) for n=2..61.

FORMULA

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.

PROG

(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) }

CROSSREFS

Sequence in context: A008051 A038424 A016437 * A016433 A049841 A038439

Adjacent sequences:  A102785 A102786 A102787 * A102789 A102790 A102791

KEYWORD

easy,nonn

AUTHOR

Cino Hilliard, Feb 25 2005

STATUS

approved

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Last modified May 25 07:51 EDT 2020. Contains 334584 sequences. (Running on oeis4.)