A126288 a(1) = 2, a(n) = n * LargestPrimeFactor(n+1) / LargestPrimeFactor(n).

2, 3, 2, 10, 3, 14, 2, 12, 15, 22, 3, 52, 7, 10, 6, 136, 3, 114, 5, 28, 33, 46, 3, 40, 65, 6, 63, 116, 5, 186, 2, 176, 51, 14, 15, 444, 19, 26, 15, 328, 7, 258, 11, 20, 207, 94, 3, 112, 35, 170, 39, 212, 3, 198, 35, 152, 87, 118, 5, 732, 31, 14, 18, 416, 55, 402, 17, 92, 21, 710

Offset

1,1

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Formula

a(n) = A006530(n+1)*A052126(n) for n>1. - Michel Marcus, May 20 2015

Example

a(6) = 6 * LargestPrimeFactor(7) / LargestPrimeFactor(6) = 6 * 7 / 3 = 14

Mathematica

a[1] := 2; a[n_] := n*FactorInteger[n + 1][[-1, 1]]/FactorInteger[n][[-1, 1]]; Table[a[n], {n, 70}] (* Ivan Neretin, May 20 2015 *)

Prog

(PARI) gpf(n) = vecmax(factor(n)[, 1]);
a(n) = if (n==1, 2, n*gpf(n+1)/gpf(n)); \\ Michel Marcus, Sep 08 2020

Crossrefs

Cf. A126286, A126287, A126289, A006530.

Sequence in context: A351251 A362988 A126286 * A205393 A075076 A333129

Adjacent sequences: A126285 A126286 A126287 * A126289 A126290 A126291

Keyword

easy,nonn

Author

Lior Manor, Dec 25 2006

Status

approved