A166923 - OEIS

%I #6 Sep 03 2014 23:44:40

%S 4,9,7,4,4,7,1,1,7,4,7,1,7,4,4,1,7,4,7,1,1,4,4,1,4,4,7,1,1,7,1,7,4,7,

%T 7,4,7,1,7,4,1,1,4,7,1,1,7,4,4,7,1,7,4,1,7,4,1,1,4,4,7,7,1,7,4,4,4,7,

%U 7,4,4,1,4,7,1,7,4,1,7,7,7,4,1,1,4,4,1,4,4,7,1,4,1,7,7,1,7,1,1,1,4,1,7,4,7

%N Digital root of prime(n)^2.

%t Table[If[(m9=Mod[Prime[n]^2,9])==0,9,m9],{n,200}]

%o (Python)

%o from sympy import prime

%o def A166923(n):

%o ....return 1 + (prime(n)**2-1) % 9 # _Chai Wah Wu_, Sep 03 2014

%Y Cf. A010888, A038194.

%K base,nonn

%O 1,1

%A _Zak Seidov_, Oct 23 2009

%E Definition corrected by _Chai Wah Wu_, Sep 03 2014