A356423 Leyland numbers which are products of two distinct primes.

57, 145, 177, 1649, 7073, 23401, 131361, 423393, 2012174, 4785713, 33555057, 43050817, 177264449, 364568617, 1073792449, 4486784401, 13877119009, 31381070257, 94143190994, 125937424601, 2552470327702, 8796093024057, 33233199005057, 130291290501553, 1628414210130481, 1853020188884609

Offset: 1

Author

Massimo Kofler, Aug 07 2022

Keywords

• nonn

Comments

A squarefree subsequence of Leyland numbers (which are numbers that can be written as a^b + b^a for a, b > 1).

Examples

			57 = 3*19 = 5^2 + 2^5.
2012174 = 2*1006087 = 9^5 + 5^9.
4486784401 = 11*407889491 = 10^9 + 9^10.
2552470327702 = 2*1276235163851 = 13^9 + 9^13.
		

Crossrefs

Intersection of A076980 and A006881.