

A165701


Numbers n such that 5^n6 is prime.


3



2, 4, 5, 6, 10, 53, 76, 82, 88, 242, 247, 473, 586, 966, 1015, 1297, 1825, 2413, 2599, 2833, 5850, 5965, 6052, 27199, 49704, 79000
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OFFSET

1,1


COMMENTS

Numbers corresponding to the a(n) for n>11 are probable prime.
If Q is a 4perfect number and gcd(Q, 5*(5^a(n)6))=1 then m=5^(a(n)1)
(5^a(n)6)*Q is a solution of the equation sigma(x)=5(x+Q)(see comment lines of the sequence A058959). 142990848 is the smallest 4perfect number m such that 5 doesn't divide m.
a(27) > 10^5.  Robert Price, Feb 03 2014


LINKS

Table of n, a(n) for n=1..26.
F. Firoozbakht, M. F. Hasler, Variations on Euclid's formula for Perfect Numbers, JIS 13 (2010) #10.3.1
H. Lifchitz, R. Lifchitz: PRP Top Records Search for 5^n6.


MATHEMATICA

Do[If[PrimeQ[5^n6], Print[n]], {n, 8888}]


PROG

(PARI) is(n)=ispseudoprime(5^n6) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Cf. A007691, A054030, A058959.
Sequence in context: A101964 A294812 A217354 * A129305 A278507 A113631
Adjacent sequences: A165698 A165699 A165700 * A165702 A165703 A165704


KEYWORD

more,nonn


AUTHOR

M. F. Hasler and Farideh Firoozbakht, Oct 30 2009


EXTENSIONS

a(24)a(26) from Robert Price, Feb 03 2014


STATUS

approved



