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A053589
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Greatest primorial number (A002110) which divides n.
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21
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1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 30, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 30, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 30, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 6
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OFFSET
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1,2
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LINKS
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FORMULA
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(End)
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EXAMPLE
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a(30) = 30 because 30=2*3*5, a(15) = 1 because 15=3*5.
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MAPLE
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N:= 1000: # to get a(1)..a(N)
P:= 1: p:= 1:
A:= Vector(N, 1):
do
p:= nextprime(p);
P:= P*p;
if P > N then break fi;
A[[seq(i, i=P..N, P)]]:= P;
od:
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MATHEMATICA
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Table[k = 1; While[Divisible[n, Times @@ Prime@ Range@ k], k++]; Times @@ Prime@ Range[k - 1], {n, 120}] (* Michael De Vlieger, Aug 30 2016 *)
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PROG
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(PARI) a(n)=my(f=factor(n), r = 1, k = 1, p); while(k<=matsize(f)[1], p=prime(k); if(f[k, 1]!=p, return(r)); r*=p; k++) ; r
a(n) = my(r = 1, p = 2); while(n/p==n\p, r*=p; p=nextprime(p+1)); r
\\ list of all terms up to n#.
lista(n) = my(l = List([1]), k, s=1); forprime(i=2, n, for(j=1, i-1, for(k=1, s, listput(l, l[k]))); l[#l]*=i; s=#l); l \\ David A. Corneth, Aug 30 2016
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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Frederick Magata (frederick.magata(AT)uni-muenster.de), Jan 19 2000
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EXTENSIONS
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More terms from Larry Reeves (larryr(AT)acm.org), Oct 02 2000
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STATUS
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approved
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