|
Search: id:A120351
|
|
|
| A120351 |
|
Even numbers such that the number of odd divisors r and the number of even divisors s are both divisors of n. |
|
+0
1
|
|
| 4, 6, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 34, 36, 38, 44, 46, 48, 52, 58, 62, 68, 72, 74, 76, 80, 82, 86, 90, 92, 94, 106, 112, 116, 118, 120, 122, 124, 126, 134, 142, 144, 146, 148, 150, 158, 160, 164, 166, 168, 172, 176, 178, 180, 188, 192, 194, 198, 202, 206
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Since s=0 if n is odd, the number n is necessarily even and then s is always a multiple of r. Note that t=r+s may not be a divisor even if both r and s are divisors. For example, if n=144, then r=3, s=12, but t=r+s=15.
|
|
FORMULA
|
a(n) = n is even, r = number of odd divisors of n, s = number of even divisors of n, are all divisors of n.
|
|
EXAMPLE
|
a(2)=16 since r=1 and s=4 are both divisors.
|
|
MAPLE
|
with(numtheory); A:=[]: N:=10^4/2: for w to 1 do for k from 2 to N do n:=2*k; S:=divisors(n); r:=nops( select(z->type(z, odd), S) ); s:=nops( select(z->type(z, even), S) ); if andmap(z -> n mod z = 0, [r, s]) then A:=[op(A), n]; print(n, r, s); fi; od od; A;
|
|
CROSSREFS
|
Cf. A033950, A049439, A057265.
Sequence in context: A109270 A137877 A163164 this_sequence A137230 A134333 A114331
Adjacent sequences: A120348 A120349 A120350 this_sequence A120352 A120353 A120354
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Walter Kehowski (wkehowski(AT)cox.net), Jun 24 2006
|
|
|
Search completed in 0.005 seconds
|
