A166923 Digital root of prime(n)^2.

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, 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, 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

Offset

1,1

Links

Table of n, a(n) for n=1..105.

Mathematica

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

Prog

(Python)
from sympy import prime
def A166923(n):
....return 1 + (prime(n)**2-1) % 9 # Chai Wah Wu, Sep 03 2014

Crossrefs

Cf. A010888, A038194.

Sequence in context: A021909 A018880 A245670 * A021205 A296425 A335089

Adjacent sequences: A166920 A166921 A166922 * A166924 A166925 A166926

Keyword

base,nonn

Author

Zak Seidov, Oct 23 2009

Extensions

Definition corrected by Chai Wah Wu, Sep 03 2014

Status

approved