OFFSET
1,3
COMMENTS
Also a(n) = x^x mod (x-2), where x = n+2.
Indices of 0's: 2^k, k>=0.
Indices of 1's: 7, 511, 713, 11023, 15553, 43873, 81079, 95263, 323593, 628153, 2275183, 6520633, 6955513, 7947583, 10817233, 12627943, 14223823, 15346303, 19852423, 27923663, 28529473, ...
Conjecture: every integer k >= 0 appears in a(n) at least once.
Each number below 69 appears at least once. Some large first occurrences: a(39806401) = 25, a(259274569) = 33, a(10571927) = 55, a(18039353) = 81. - Charles R Greathouse IV, Jul 21 2015
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = 2^(n+2) mod n.
EXAMPLE
a(3) = 2^5 mod 3 = 32 mod 3 = 2.
MAPLE
MATHEMATICA
Table[PowerMod[2, n+2, n], {n, 79}] (* Alonso del Arte, Jul 22 2012 *)
PROG
(Python)
for n in range(1, 99):
print(2**(n+2) % n, end=', ')
(PARI) A212844(n)=lift(Mod(2, n)^(n+2)) \\ M. F. Hasler, Jul 23 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Jul 22 2012
STATUS
approved