A261210 a(n) = gpf(1 + Product_{k=0..4} prime(n+k)), where gpf is greatest prime factor and prime(i) is the i-th prime.

2311, 1877, 163, 80831, 12647, 6967, 139, 3633983, 1657, 15473, 2970049, 933853, 64776587, 99767, 21067, 84961, 1524137, 820319, 157229, 489427, 2066140207, 71899, 15287, 1680583, 769117, 55732973, 52889, 225941, 4678959379, 1491686591, 87701

Offset: 1

Author

Anders Hellström, Aug 12 2015

Keywords

• nonn

Links

• Anders Hellström, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A006530, A046303.

Programs

Mathematica

Array[FactorInteger[1 + Product[Prime[# + k], {k, 0, 4}]][[-1, 1]] &, {31}] (* Michael De Vlieger, Aug 19 2015 *)

PARI

gpf(n)=vecmax(factor(n)[, 1]);
first(m)=vector(m, i, gpf(1+prod(j=0,4,prime(i+j))));

Formula

a(n) = A006530(1+A046303(n)). - Michel Marcus, Aug 13 2015