A112600 Smallest prime factor of A111392(n).

2, 5, 11, 37, 13, 23, 19, 23, 37, 127, 47, 61, 61, 47, 67, 61, 277, 83, 79, 97, 127, 83, 101, 131, 269, 109, 131, 109, 113, 157, 137, 181, 157, 181, 151, 173, 173, 179, 173, 211, 223, 251, 193, 197, 223, 233, 223, 251, 271, 241, 239, 269, 293, 281, 313, 347, 293

Offset: 1

Author

Yasutoshi Kohmoto, Dec 15 2005

Keywords

• nonn

Comments

For all i, if iA111392(n))=1, where p_i is i-th prime.

A111392: a(n) = Product_{i=1..n-1} (Product_{k=1..i} p_k + Product_{k=i+1..n} p_k). - Robert G. Wilson v, Dec 22 2005

Crossrefs

Cf. A111392.

Programs

Mathematica

f[n_] := Product[(Product[Prime[k], {k, i}] + Product[Prime[k], {k, i + 1, n}]), {i, n - 1}]; f[1] = 2; g[n_] := Block[{k = 1}, While[Mod[f[n], Prime[k]] != 0, k++ ]; Prime@k]; Array[g, 20] (* Robert G. Wilson v *)

Extensions

More terms from Robert G. Wilson v, Dec 22 2005