A186887 The smallest infinitary divisor of the n-th infinitary perfect number, which is a perfect square >1.

4, 9, 9, 16, 4, 4, 9, 16, 4, 81, 4, 4, 16, 25, 9, 4

Offset

2,1

Comments

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

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

1;

1,4;

1,9;

1,9,16,144;

1,16,81,1296;

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

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

1,9,256,2304;

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

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

1,81,256,20736;

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

Links

Table of n, a(n) for n=2..17.

Crossrefs

Cf. A007357

Sequence in context: A157300 A100555 A250126 * A140978 A106410 A065737

Adjacent sequences: A186884 A186885 A186886 * A186888 A186889 A186890

Keyword

nonn

Author

Vladimir Shevelev, Feb 28 2011

Status

approved