1,6

In this sequence p < n, but p^k with k>=2 may be equal to n.

a(n) = 1 iff n = 2^k, k >= 0 or n is prime;

1 < a(n) < n iff n is even composite and not a power of 2;

a(n) = n iff n is nonprime (unit or composite) odd.

Daniel Forgues, Table of n, a(n) for n=1..100000

Cf. A171487, A000265, A010051.

Sequence in context: A142992 A145905 A336859 * A144183 A050153 A294950

Adjacent sequences: A171432 A171433 A171434 * A171436 A171437 A171438

nonn

Daniel Forgues, Dec 09 2009

Edited by Daniel Forgues, Dec 10 2009

approved