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 A131553 a(n) = Product_{k=1..n, gcd(k,n)=1} (1+k). 0
 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; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE The positive integers that 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. MAPLE 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, 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, Aug 28 2007 MATHEMATICA Table[Times @@ (1 + Select[Range[n], GCD[ #, n] == 1 &]), {n, 1, 40}] (* Stefan Steinerberger, Sep 14 2007 *) PROG (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 Conroy, Sep 05 2007 CROSSREFS Sequence in context: A169970 A334499 A201499 * A277510 A169800 A094485 Adjacent sequences:  A131550 A131551 A131552 * A131554 A131555 A131556 KEYWORD nonn AUTHOR Leroy Quet, Aug 26 2007 STATUS approved

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Last modified June 1 20:49 EDT 2020. Contains 334765 sequences. (Running on oeis4.)