|
|
A087991
|
|
Number of non-palindromic divisors of n.
|
|
12
|
|
|
0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 0, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 0, 2, 1, 3, 1, 2, 2, 3, 1, 3, 1, 0, 2, 2, 1, 4, 1, 3, 2, 3, 1, 3, 0, 3, 2, 2, 1, 6, 1, 2, 2, 3, 2, 0, 1, 3, 2, 4, 1, 5, 1, 2, 3, 3, 0, 4, 1, 5, 2, 2, 1, 6, 2, 2, 2, 0, 1, 6, 2, 3, 2, 2, 2, 6, 1, 3, 0, 5, 0, 4, 1, 4, 4
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,20
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
n=132: divisors={1,2,3,4,6,11,12,22,33,44,66,132},
revdivisors={1,2,3,4,6,11,21,22,33,44,66,231}, a[132]=2;
so two of 12 divisors of n are non-palindromic:{21,132}.
|
|
MATHEMATICA
|
palQ[n_] := Reverse[x = IntegerDigits[n]] == x; Table[Count[Divisors[n], _?(! palQ[#] &)], {n, 105}] (* Jayanta Basu, Aug 10 2013 *)
|
|
PROG
|
(Python)
def ispal(n):
w=str(n)
return w==w[::-1]
s = 0
for i in range(1, n+1):
if n%i==0 and not ispal(i):
s+=1
return s
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|