A109216 -id:A109216 - cp's OEIS frontend

A109215 Smallest factor of 3^(2n)+(2n)^3.

17, 5, 3, 11, 11, 3, 677, 17, 3, 83, 23, 3, 5, 29, 3, 1049, 23, 3, 307, 41, 3, 5, 5, 3, 41, 53, 3, 523347633027360537213687137, 59, 3, 11, 5, 3, 227, 71, 3, 630023, 101, 3, 29, 47, 3, 5, 89, 3, 1957243, 11, 3, 251, 101, 3, 5, 5, 3, 29, 113, 3, 1289, 11, 3, 701, 5, 3, 307

Offset: 1

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Zak Seidov, Jun 24 2005

base
nonn

For n=1 and 28 we have the only two known cases where 3^(2n)+(2n)^3 is prime: 17 and 523347633027360537213687137. Cases n=3*m are trivial and may be omitted.
There are no further cases when 3^(2n)+(2n)^3 is prime up to n = 3500. Hugo Pfoertner, Jun 25 2005
n = 5056 gives a probable prime. Hans Havermann, Jun 24 2005

Cf. A109216.

Table[With[{k=3}, FactorInteger[n^k+k^n]][[1, 1]], {n, 2, 100, 2}]

More terms from Robert G. Wilson v, Jun 25 2005

cp's OEIS Frontend

A109215 Smallest factor of 3^(2n)+(2n)^3.

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