OFFSET
1,2
LINKS
Ivan N. Ianakiev, Table of n, a(n) for n = 1..1000
EXAMPLE
The sum of the digital roots of the first four primes is prime (2+3+5+7=17), therefore 4 is in the sequence.
MATHEMATICA
Select[Range[1000], PrimeQ[Sum[Mod[Prime[i], 9], {i, 1, #}]]&]
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Ivan N. Ianakiev, Oct 08 2014
EXTENSIONS
Edited. Name specified. - Wolfdieter Lang, Oct 30 2014
STATUS
approved