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A222085
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Sum of the least divisors of n whose LCM is equal to n.
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6
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1, 3, 4, 7, 6, 6, 8, 15, 13, 8, 12, 10, 14, 10, 9, 31, 18, 21, 20, 12, 11, 14, 24, 24, 31, 16, 40, 14, 30, 11, 32, 63, 15, 20, 13, 25, 38, 22, 17, 20, 42, 19, 44, 18, 18, 26, 48, 52, 57, 43, 21, 20, 54, 66, 17, 22, 23, 32, 60, 15, 62, 34, 20, 127, 19, 23, 68
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OFFSET
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1,2
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LINKS
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EXAMPLE
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The divisors of 20 are 1, 2, 4, 5, 10, 20 while the least divisors of 20 whose LCM is equal to 20 are 1, 2, 4, 5. Then a(20) = 1+2+4+5 = 12.
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MAPLE
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with(numtheory);
local a, b, c, j, n, v; print(1);
for n from 2 to q do a:=ifactors(n)[2]; b:=nops(a); c:=0;
for j from 1 to b do if a[j][1]^a[j][2]>c then c:=a[j][1]^a[j][2]; fi; od;
a:=op(sort([op(divisors(n))])); b:=nops(divisors(n)); v:=0;
for j from 1 to b do v:=v+a[j]; if a[j]=c then break; fi; od; print(v);
od; end:
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MATHEMATICA
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s[n_] := Module[{sum=0, L=1}, Do[sum+=d; L = LCM[L, d]; If[L == n, Break[]], {d, Divisors[n]}]; sum]; Array[s, 67] (* Amiram Eldar, Nov 05 2019 *)
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PROG
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(PARI) a(n)=my(s, L=1); fordiv(n, d, s+=d; L=lcm(L, d); if(L==n, return(s))) \\ Charles R Greathouse IV, Feb 14 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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