A248554 - OEIS

%I #9 Oct 30 2014 07:32:12

%S 1,2,4,5,6,7,9,11,17,37,41,47,59,61,79,85,87,98,104,109,112,126,132,

%T 141,142,143,151,152,158,173,183,184,191,192,204,208,210,212,215,221,

%U 226,227,236,243,251,256,274,279,306,314,325,334,356,365,375,382,387,401,403,419,437,452,473,483,488

%N Numbers k such that the sum of the digital roots of the first k primes is also prime; increasingly sorted.

%H Ivan N. Ianakiev, <a href="/A248554/b248554.txt">Table of n, a(n) for n = 1..1000</a>

%e The sum of the digital roots of the first four primes is prime (2+3+5+7=17), therefore 4 is in the sequence.

%t Select[Range[1000],PrimeQ[Sum[Mod[Prime[i],9],{i,1,#}]]&]

%Y Cf. A000040, A010888.

%K base,easy,nonn

%O 1,2

%A _Ivan N. Ianakiev_, Oct 08 2014

%E Edited. Name specified. - _Wolfdieter Lang_, Oct 30 2014