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A183147
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1 together with the numbers with property that at least two successive of their divisors are odd or even.
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1
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1, 3, 4, 5, 7, 8, 9, 11, 12, 13, 15, 16, 17, 19, 20, 21, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 35, 36, 37, 39, 40, 41, 43, 44, 45, 47, 48, 49, 51, 52, 53, 55, 56, 57, 59, 60, 61, 63, 64, 65, 67, 68, 69, 70, 71, 72, 73, 75, 76, 77, 79, 80, 81, 83, 84, 85, 87, 88, 89, 90, 91, 92, 93, 95, 96, 97, 99, 100
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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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12 is in the sequence because its divisors are 1, 2, 3, 4, 6, 12 and then we can see that the successive divisors 4, 6, and 12 are even numbers.
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MAPLE
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isA183147 := proc(n)
local di, i ;
if n = 1 then
return true;
end if;
di := sort(convert(numtheory[divisors](n), list)) ;
for i from 1 to nops(di)-1 do
if (op(i+1, di)-op(i, di)) mod 2 = 0 then
return true;
end if;
end do;
return false;
end proc:
for n from 1 to 100 do
if isA183147(n) then
printf("%d, ", n);
end if;
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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