A137807 - OEIS

%I #9 Jan 20 2022 13:47:06

%S 4,9,5,9,1,9,9,1,9,1,1,9,1,9,9,9,1,1,9,1,9,1,9,1,9,1,9,9,1,9,9,1,9,1,

%T 1,1,9,9,9,9,1,1,1,9,9,1,1,9,9,1,9,1,1,1,9,9,1,1,9,1,9,9,9,1,9,9,1,9,

%U 9,1,9,1,9,9,1,9,1,9,1,1,1,1,1,9,1,9,1,9,1,9,9,1,9,1,1,9,1,1,9,1,9,9,9,1,1

%N Final digit of prime(n)^2.

%C Euler and Sadek ask whether the sequence, interpreted as the decimal expansion N = 0.49591..., is rational or irrational. - _Charles R Greathouse IV_, Apr 19 2010

%D R. Euler and J. Sadek, A number that gives the unit digit of n^n. Journal of Recreational Mathematics, 29:3 (1998), pp. 203-204. [From _Charles R Greathouse IV_, Apr 19 2010]

%F a(n) = A010879(A001248(n)). - _R. J. Mathar_, May 03 2008

%p A001248 := proc(n) ithprime(n)^2 ; end: A010879 := proc(n) n mod 10 ; end: A137807 := proc(n) A010879(A001248(n)) ; end: seq(A137807(n),n=1..140) ; # _R. J. Mathar_, May 03 2008

%t Mod[Prime[Range[110]]^2,10] (* _Harvey P. Dale_, Jan 20 2022 *)

%K nonn,base

%O 1,1

%A _Paul Curtz_, Apr 29 2008

%E More terms from _R. J. Mathar_, May 03 2008