A186887 - OEIS

%I #10 Aug 09 2015 15:57:59

%S 4,9,9,16,4,4,9,16,4,81,4,4,16,25,9,4

%N The smallest infinitary divisor of the n-th infinitary perfect number, which is a perfect square >1.

%C 6 = A007357(1) is only squarefree infinitary perfect number. In consequence, a(n)>=4 for n>1.

%C An irregular table with the infinitary divisors of A007357(n) which are also perfect squares starts in row n>=1 as

%C 1;

%C 1,4;

%C 1,9;

%C 1,9,16,144;

%C 1,16,81,1296;

%C 1,4,9,16,25,36,64,100,144,225,400,576,900,1600,3600,14400;

%C 1,4,16,64,81,324,1296,5184;

%C 1,9,256,2304;

%C 1,16,25,49,81,400,784,1225,1296,2025,3969,19600,32400,63504,99225,1587600;

%C 1,4,16,25,49,64,81,100,196,324,400,784,1225,1296,1600,2025,3136,3969,4900,...

%C 1,81,256,20736;

%C The current sequence consists of the second column of this table.

%Y Cf. A007357

%K nonn

%O 2,1

%A _Vladimir Shevelev_, Feb 28 2011