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A192284
Numbers n such that the average of the anti-divisors of n is an integer.
2
3, 4, 6, 8, 9, 11, 15, 16, 18, 19, 20, 26, 29, 30, 34, 36, 37, 38, 47, 49, 51, 63, 64, 68, 69, 82, 93, 94, 95, 96, 106, 117, 120, 121, 131, 134, 135, 141, 155, 169, 174, 186, 187, 190, 191, 197, 200, 203, 206, 224, 226, 244, 252, 257, 271, 272, 274, 276, 289
OFFSET
1,1
COMMENTS
Like A003601 but using anti-divisors
LINKS
EXAMPLE
Anti-divisors of 38 are 7: 3, 4, 5, 7, 11, 15, 25. Their sum is 70 and 70/7=10 that is integer.
MAPLE
with(numtheory);
P:=proc(n)
local a, b, i, k;
for i from 3 to n do
a:=0; b:=0;
for k from 2 to i-1 do
if abs((i mod k)- k/2) < 1 then a:=a+k; b:=b+1; fi;
od;
if trunc(a/b)=a/b then print(i); fi;
od;
end:
P(1000);
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Jul 20 2011
STATUS
approved