

A183147


1 together with the numbers with property that at least two successive of their divisors are odd or even.


1



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

1,2


LINKS

Table of n, a(n) for n=1..78.
Wikipedia, Table of divisors


EXAMPLE

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.


MAPLE

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;
end do; # R. J. Mathar, Sep 30 2011


CROSSREFS

Complement of A182991, for n > 1.
Cf. A182996.
Sequence in context: A285958 A179779 A284679 * A074227 A122906 A042965
Adjacent sequences: A183144 A183145 A183146 * A183148 A183149 A183150


KEYWORD

nonn,easy


AUTHOR

Omar E. Pol, Aug 04 2011


STATUS

approved



