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Iterated sum-of-digits of A078403(n).
3

%I #9 Nov 17 2019 15:54:43

%S 2,3,5,7,2,5,2,5,7,2,5,7,7,2,7,2,5,5,2,5,7,5,2,2,7,2,5,7,5,2,7,2,5,5,

%T 7,2,7,5,7,2,7,5,2,5,5,7,7,2,7,2,2,5,5,7,5,2,2,5,7,5,7,2,5,2,7,2,7,7,

%U 7,5,5,5,2,2,7,2,5,7,2,2,5,2,5,2,7,5,2,5,7,5,7,7,7,2,5,2,7,2,2,5,7,2,5,7,7

%N Iterated sum-of-digits of A078403(n).

%H Cino Hilliard, <a href="/A078400/a078400.txt">Proof of the Digital Root Theorem</a>, posted on Yahoo group B2LCC, Feb 17 2003

%o (PARI) drp(n) = { forprime(x=2,n, r = x%9; if(isprime(r), print1(r" "); ); ); }

%Y Cf. A038194, A078403.

%K easy,nonn,base

%O 1,1

%A _Cino Hilliard_, Dec 24 2002

%E More terms from _Joshua Zucker_, Jul 24 2006