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Search: id:A131553
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| A131553 |
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a(n) = product{1<=k<=n, GCD(k,n)=1} (1+k). |
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+0
1
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| 2, 2, 6, 8, 120, 12, 5040, 384, 12960, 640, 39916800, 1152, 6227020800, 80640, 5443200, 10321920, 355687428096000, 290304, 121645100408832000, 38707200, 384758035200, 6812467200, 25852016738884976640000, 139345920
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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The positive integers which are <= 9 and are coprime to 9 are 1,2,4,5,7,8.
So a(9) = (1+1)(1+2)(1+4)(1+5)(1+7)(1+8) = 2*3*5*6*8*9 = 12960.
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MAPLE
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a:=proc(n) local p, k: p:=1: for k to n do if gcd(k, n)=1 then p:=p*(1+k) else end if end do: p end proc: seq(a(n), n=1..22); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Sep 05 2007
for n to 25 do pr:=1: for k to n do if gcd(k, n)=1 then pr:=pr*(1+k) else end if end do: a[n]:=pr end do: seq(a[n], n=1..25); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 28 2007
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MATHEMATICA
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Table[Times @@ (1 + Select[Range[n], GCD[ #, n] == 1 &]), {n, 1, 40}] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Sep 14 2007
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PROGRAM
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(PARI) rr(n) = pp=1; for(i=1, n, if(gcd(i, n)==1, pp=pp*(1+i))); return(pp); for(j=1, 60, print1(rr(j), ", ")) - Matthew M. Conroy, Sep 05 2007
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CROSSREFS
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Sequence in context: A074933 A003178 A079494 this_sequence A094485 A021819 A000021
Adjacent sequences: A131550 A131551 A131552 this_sequence A131554 A131555 A131556
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Aug 26 2007
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