A108077 Largest prime p such that p-1 divides n.

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

Offset: 1

Author

Philippe Deléham, Jul 20 2005

Keywords

• nonn
• easy

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384
• Antti Karttunen, Data supplement: n, a(n) computed for n = 1..100000

Crossrefs

Largest term in row n of A108939.

Programs

Maple

with(numtheory): for n from 1 to 110 do div:=divisors(n): A:=[seq(div[j]+1,j=1..tau(n))]: B:={}: for i from 1 to tau(n) do if isprime(A[i])=true then B:=B union {A[i]} else B:=B: fi: od: C:=convert(B,list): a[n]:=C[nops(C)] od: seq(a[n],n=1..110); # Emeric Deutsch, Aug 05 2005

PARI

A108077(n) = fordiv(n,d,if(isprime(1+(n/d)), return(1+(n/d)))); \\ Antti Karttunen, Dec 19 2018

Extensions

More terms from Emeric Deutsch, Aug 05 2005