OFFSET
0,3
COMMENTS
The next term is too large to include.
Last digit of a(n) is 5 or 9 for n>1. It appears that a(4k) == 4 mod 5 and a(4k+1) == a(4k+2) == a(4k+3) == 0 mod 5.
p divides a(p) for prime p>2. Composite numbers n such that n divides a(n) are listed in A127643 = {15,51,65,85,185,221,255,341,451,533,561,595,645,679,771,...}. - Alexander Adamchuk, Jan 22 2007
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..8
FORMULA
a(n) = ((2^n - 1)^(2^n) - 1)/(2^n)^2.
a(n) = A085606(2^n)/(2^n)^2.
MATHEMATICA
Table[((2^n-1)^(2^n)-1)/(2^n)^2, {n, 0, 7}]
PROG
(PARI) for(n=0, 7, print1(((2^n - 1)^(2^n) - 1)/(2^n)^2, ", ")) \\ G. C. Greubel, Oct 26 2017
(Magma) [((2^n - 1)^(2^n) - 1)/(2^n)^2: n in [0..7]]; // G. C. Greubel, Oct 26 2017
CROSSREFS
KEYWORD
sign
AUTHOR
Alexander Adamchuk, Nov 13 2006
EXTENSIONS
More terms from Alexander Adamchuk, Jan 22 2007
STATUS
approved