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 A300951 a(n) = Product_{j=1..floor(n/2)} p(j) where p(j) = j if j is prime else 1. 1
 1, 1, 1, 1, 2, 2, 6, 6, 6, 6, 30, 30, 30, 30, 210, 210, 210, 210, 210, 210, 210, 210, 2310, 2310, 2310, 2310, 30030, 30030, 30030, 30030, 30030, 30030, 30030, 30030, 510510, 510510, 510510, 510510, 9699690, 9699690, 9699690, 9699690, 9699690, 9699690, 9699690 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS a(4*n+2)=a(4*n+3)=a(4*n+4)=a(4*n+5) for n >= 1. - Robert Israel, Mar 16 2018 The length of the n-th run is given by 2*A054541(n). - Michel Marcus, Mar 17 2018 LINKS Robert Israel, Table of n, a(n) for n = 0..4713 FORMULA a(n) = A002110(A056172(n)). - Robert Israel, Mar 16 2018 MAPLE a := n -> mul(`if`(isprime(j), j, 1), j=1..iquo(n, 2)): seq(a(n), n=0..44); # Alternative: f:= proc(n) option remember;   if n::even and isprime(n/2) then procname(n-1)*n/2 else procname(n-1) fi end proc: f(0):= 1: map(f, [\$0..100]); # Robert Israel, Mar 16 2018 PROG (PARI) a(n) = prod(i=1, n\2, if(isprime(i), i, 1)); \\ Altug Alkan, Mar 16 2018 CROSSREFS Cf. A002110, A054541, A056172, A089026. Sequence in context: A319865 A140219 A259225 * A077081 A084700 A122766 Adjacent sequences:  A300948 A300949 A300950 * A300952 A300953 A300954 KEYWORD nonn AUTHOR Peter Luschny, Mar 16 2018 STATUS approved

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Last modified October 22 07:48 EDT 2019. Contains 328315 sequences. (Running on oeis4.)