A281072 - OEIS

%I #12 Jan 19 2017 23:49:06

%S 1,2,4,4,6,6,10,10,10,10,36,36,66,66,196,196,196,196,568,568,568,568,

%T 1008,1008,1288,1288,1288,1288,8398,8398,8730,8730,50688,50688,124738,

%U 124738,124738,124738,155296,155296,155296,155296,155296,155296,155296,155296,1784476,1784476

%N Smallest number k > 0 such that b - r is even or r = 0 for all b = 1..n, r == k mod b.

%C a(n) is the smallest number for which A281071(a(n)) is greater than or equal to n.

%H Martin Janecke, <a href="/A281072/b281072.txt">Table of n, a(n) for n = 1..88</a>

%e a(3) = 4 because

%e   1 mod 2 = 1 where r > 0 and 2 - 1 is odd;

%e   2 mod 3 = 2 where r > 0 and 3 - 2 is odd;

%e   3 mod 2 = 1 where r > 0 and 2 - 1 is odd;

%e   4 mod 1 = 0 where r = 0,

%e   4 mod 2 = 0 where r = 0,

%e   4 mod 3 = 1 where 3 - 1 is even.

%Y Cf. A281071.

%K nonn,easy

%O 1,2

%A _Martin Janecke_, Jan 14 2017