OFFSET
1,1
COMMENTS
Beyond n = 4, a(n) is believed to coincide with A062339.
Only correct for n >= 4 if an undiscovered prime of digit sum two (which would have to be a member of A080176) does not exist; this is conjectured but not proved. - Jeppe Stig Nielsen, Mar 30 2018
EXAMPLE
There are only three primes with a digit sum of 2, and those are 2, 11, 101. Therefore these three primes are the first three terms of this sequence.
There is only one prime with a digit sum of 3, and that's 3 itself. Any higher number with a digit sum of 3 is a nontrivial multiple of 3 and therefore composite.
Then follows the first prime with a digit sum of 4, which is 13.
MATHEMATICA
Prime@ Flatten@ Values@ Take[KeySort@ PositionIndex[Total@ IntegerDigits@ # & /@ Prime@ Range[10^7]], 3] (* Michael De Vlieger, Apr 07 2018 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Lekraj Beedassy, Mar 04 2009
EXTENSIONS
Comment edited by Robert Israel, Dec 28 2015
STATUS
approved