

A125570


Numbers n such that Sum_(x=1..n) (x1)*6^(x1))/6 is prime.


0



3, 7, 8, 19, 69, 77, 104, 107, 162, 163, 399, 4787, 4818
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

No more terms through 10^4.
Note that Sum(x=1,n,(x1)*6^(x1))/6 = (6^(n1)*(5*n6)+1)/25. Therefore this sequence consists of n such that (6^(n1)*(5*n6)+1)/25 is prime.  Max Alekseyev, Oct 18 2008


LINKS

Table of n, a(n) for n=1..13.


MATHEMATICA

s = 0; Do[s += (x1)*6^(x1)/6; If[PrimeQ[s], Print[x]], {x, 10^4}]


CROSSREFS

Cf. A119529.
Sequence in context: A122227 A259571 A291212 * A268111 A244532 A037208
Adjacent sequences: A125567 A125568 A125569 * A125571 A125572 A125573


KEYWORD

hard,more,nonn


AUTHOR

Ryan Propper, Jan 01 2007


STATUS

approved



