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

1,1

Comments

For all i, if i<n+2 then GCD(p_i,A111392(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

Links

Table of n, a(n) for n=1..57.

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 *)

Crossrefs

Cf. A111392.

Sequence in context: A295495 A343463 A130622 * A156014 A268397 A261438

Adjacent sequences: A112597 A112598 A112599 * A112601 A112602 A112603

Keyword

nonn

Author

Yasutoshi Kohmoto, Dec 15 2005

Extensions

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

Status

approved