A117366 - OEIS

A117366

a(n) = smallest prime greater than the largest prime dividing n.

2, 3, 5, 3, 7, 5, 11, 3, 5, 7, 13, 5, 17, 11, 7, 3, 19, 5, 23, 7, 11, 13, 29, 5, 7, 17, 5, 11, 31, 7, 37, 3, 13, 19, 11, 5, 41, 23, 17, 7, 43, 11, 47, 13, 7, 29, 53, 5, 11, 7, 19, 17, 59, 5, 13, 11, 23, 31, 61, 7, 67, 37, 11, 3, 17, 13, 71, 19, 29, 11, 73, 5, 79, 41, 7, 23, 13, 17, 83, 7

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OFFSET

1,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A151800(A006530(n)). - Reinhard Zumkeller, Apr 06 2015

a(n) = A000040(A159081(n)). - Antti Karttunen, Jan 15 2020

EXAMPLE

5 is the largest prime dividing 10. So a(10) is the smallest prime > 5, which is 7.

MATHEMATICA

Table[Prime[PrimePi[FactorInteger[n][[Length[FactorInteger[n]]]][[1]]]+1], {n, 2, 80}], 2, 1] (* Stefan Steinerberger, Apr 09 2006 *)