A309747 Numbers k such that k^k + (k+1)^(k+1) is a semiprime.

5, 7, 9, 11, 14, 21, 37, 38, 39, 57, 90, 97, 162

Offset: 1

Author

Hugo Pfoertner, Aug 15 2019

Keywords

• nonn
• more
• hard

Comments

Numbers k such that A217435(k+1) = 2.

a(14) >= 235, see FactorDB link.

Examples

			a(1) = 5 because 5^5 + 6^6 = 49781 = 67*743.
		

Links

• FactorDB, Status of 235^235+236^236.
• Walter Nissen, Addendum to Prime factors of n^n + (n+1)^(n+1), Table F, 2014-01-07.

Crossrefs

Cf. A056187, A056788, A056790, A217435.

Programs

PARI

for(k=0,40,if(bigomega(k^k+(k+1)^(k+1))==2,print1(k,", ")))