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A222085 Sum of the least divisors of n whose LCM is equal to n. 6
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..1000

EXAMPLE

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.

MAPLE

with(numtheory);

A222085:=proc(q)

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:

A222085(100000000);

PROG

(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

CROSSREFS

Cf. A000005, A000961, A001358, A003418, A005179, A024619, A034444, A077610, A222084.

Sequence in context: A105827 A230289 A023888 * A187793 A284326 A117553

Adjacent sequences:  A222082 A222083 A222084 * A222086 A222087 A222088

KEYWORD

nonn

AUTHOR

Paolo P. Lava, Feb 11 2013

STATUS

approved

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Last modified April 22 11:46 EDT 2019. Contains 322330 sequences. (Running on oeis4.)