A274910 Largest prime factor of 11^n - 1.

5, 5, 19, 61, 3221, 37, 45319, 7321, 1772893, 13421, 1806113, 1117, 3158528101, 1623931, 195019441, 6304673, 50544702849929377, 1772893, 6115909044841454629, 212601841, 45319, 1806113, 3740221981231, 20113, 1856458657451, 3158528101, 5559917315850179173

Offset: 1

Author

Vincenzo Librandi, Jul 11 2016

Keywords

• nonn

Examples

			11^4 - 1 = 14640 = 2^4*3*5*61, so a(4) = 61.
		

Links

• Table of n, a(n) for n = 1..316
• J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.

Crossrefs

Cf. A006530, A024127.

Cf. similar sequences listed in A274906.

Programs

Magma

[Maximum(PrimeDivisors(11^n-1)): n in [1..40]];

Mathematica

Table[FactorInteger[11^n - 1][[-1, 1]], {n, 40}]

Formula

a(n) = A006530(A024127(n)).

Extensions

Terms to a(70) in b-file from Vincenzo Librandi, Jul 13 2016

a(71)-a(306) in b-file from Amiram Eldar, Feb 08 2020

a(307)-a(316) in b-file from Max Alekseyev, Apr 25 2022, Oct 26 2023