A081317 Primes p such that p divides 10^n-1, p is the largest prime producing decimal fraction period n and p is not the largest prime dividing 10^n-1.

13, 52579, 8779, 2161, 69857, 909090909090909091, 459691, 549797184491917, 14175966169, 183411838171, 296557347313446299, 388847808493, 3404193829806058997303, 8985695684401, 297262705009139006771611927

Offset: 1

Author

Hugo Pfoertner, Mar 18 2003

Keywords

• nonn
• base

Examples

			a(1)=13 because the largest factor 37 in the factorization of 10^6-1=999999=3^3*7*11*13*37 already occurs in the factorization of 10^3-1=3^3*37 and produces only a decimal fraction period of 3. 1/37=0.027027027...., 1/13=0.0769230769230...
		

Links

• Max Alekseyev, Table of n, a(n) for n = 1..54 (first 50 terms from Ray Chandler)
• Sam Wagstaff, The Cunningham Project, The Main Tables

Crossrefs

Cf. A005422, A003020, A061075, A081318.

Formula

Numbers in A061075(n) such that A061075(n) is not equal to A005422(n). The corresponding values of n are given in A081318.

a(n) = A061075(A081318(n)). - Max Alekseyev, Apr 27 2022

Extensions

More terms from Hans Havermann, May 31 2003