A062573 - OEIS

A062573

Numbers k such that 7^k - 6^k is prime.

2, 3, 7, 29, 41, 67, 1327, 1399, 2027, 69371, 86689, 355039 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,1`
	COMMENTS	`Terms greater than 1000 often correspond only to strong probable primes.`
	LINKS	`Table of n, a(n) for n=1..12.` `Henri & Renaud Lifchitz, Top probable primes of the form 7^p-6^p`
	EXAMPLE	`7^2 - 6^2 = 49 - 36 = 13, which is prime, so 2 is in the sequence.` `7^3 - 6^3 = 343 - 216 = 127, which is prime, so 3 is in the sequence.`
	MATHEMATICA	`Select[Range[100], PrimeQ[7^# - 6^#] &] (* Alonso del Arte, Sep 04 2013 *)`
	PROG	`(PARI) is(n)=ispseudoprime(7^n-6^n) \\ Charles R Greathouse IV, Feb 20 2017`
	CROSSREFS	`Cf. A000043, A057468, A059801, A059802, A062572-A062666.` `Sequence in context: A270347 A060412 A276665 * A019435 A061092 A084435` `Adjacent sequences: A062570 A062571 A062572 * A062574 A062575 A062576`
	KEYWORD	`nonn,hard`
	AUTHOR	`Mike Oakes, May 18 2001, May 19 2001`
	EXTENSIONS	`Two more terms (69371 and 86689) found by Predrag Minovic in 2004 corresponding to probable primes with 58626 and 73261 digits. - Jean-Louis Charton, Oct 06 2010` `New term 355039 found by Jean-Louis Charton in May 2011 corresponding to a probable prime with 300043 digits.`
	STATUS	`approved`