2,1

Max Alekseyev, Table of n, a(n) for n = 2..1000

R. Munafo, Smallest positive integer m such that 2^3^4^5^...^n == m mod n

a(n) = n if n is a power of 2; otherwise a(n) = (2^3^4^5^...^n) mod n = A213013(n). [From Max Alekseyev, Jun 02 2012]

2^3^4^5 = 2^3^1024. But 3 == -1 (mod 4), so 3^1024 == 1 (mod 4), so 2^3^1024 == 2^1 (mod 5) since 2^4 == 1 (mod 5). Thus a(5) = 2.

Sequence in context: A021450 A239675 A289827 * A340675 A097884 A094818

Adjacent sequences: A092185 A092186 A092187 * A092189 A092190 A092191

nonn,nice

N. J. A. Sloane, following a suggestion of J. H. Conway, Apr 02 2004

More terms from Robert Munafo, Apr 11 2004

approved