A181687 Numbers n such that the number of odd divisors of (2n)^2 is an odd divisor of (2n)^2, and the number of even divisors of (2n)^2 is an even divisor of (2n)^2.

1, 2, 3, 6, 8, 12, 15, 21, 24, 25, 30, 33, 39, 42, 45, 50, 51, 57, 66, 69, 75, 78, 81, 87, 90, 93, 96, 102, 111, 114, 120, 123, 128, 129, 138, 141, 150, 159, 162, 168, 174, 177, 180, 183, 186, 189, 200, 201, 213, 219, 222, 225, 237, 240, 246, 249, 258, 264, 267, 282, 291, 300

Offset: 1

Author

Nathaniel Johnston, Nov 17 2010

Keywords

• easy
• nonn

Comments

A016742(a(n)) = A181795(n)

Programs

Maple

for j from 1 to 300 do
   y:=(2*j)^2:evdiv:=0:oddiv:=0:
   for k in divisors(y) do
      if(k mod 2=0)then evdiv:=evdiv+1:else oddiv:=oddiv+1:fi:
   od:
   if(type(y/evdiv,integer) and type(y/oddiv,integer))then
      print(j);
   fi;
od: