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

1,1

Comments

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

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

Links

Table of n, a(n) for n=1..13.

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.

Example

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

Prog

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

Crossrefs

Cf. A056187, A056788, A056790, A217435.

Sequence in context: A064077 A026282 A314375 * A080384 A086398 A356052

Adjacent sequences: A309744 A309745 A309746 * A309748 A309749 A309750

Keyword

nonn,more,hard

Author

Hugo Pfoertner, Aug 15 2019

Status

approved