A104212 Sum of the digits of n when the sum is prime.

2, 3, 5, 7, 2, 3, 5, 7, 2, 3, 5, 7, 11, 3, 5, 7, 11, 5, 7, 11, 13, 5, 7, 11, 13, 7, 11, 13, 7, 11, 13, 11, 13, 17, 11, 13, 17, 2, 3, 5, 7, 2, 3, 5, 7, 11, 3, 5, 7, 11, 5, 7, 11, 13, 5, 7, 11, 13, 7, 11, 13, 7, 11, 13, 11, 13, 17, 11, 13, 17, 11, 13, 17, 19, 2, 3, 5, 7, 11, 3, 5, 7, 11, 5, 7, 11

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

sd:= n -> convert(convert(n, base, 10), `+`):
select(isprime, map(sd, [$1..400])); # Robert Israel, Jan 20 2019

Mathematica

Select[Array[Total@ IntegerDigits@ # &, 300], PrimeQ] (* Michael De Vlieger, Jan 20 2019 *)

Prog

(PARI) sdprime(n) = { local(x, y); for(x=1, n, y=sumdigits(x); if(isprime(y), print1(y", ") ) ) } sumdigits(n) = \ The sum of the digits of n { local(x, j, s=0); x=digits(n); for(j=1, length(x), s+=x[j]; ); return(s) } digits(n) = \ The vector of the digits of n { return(eval(Vec(Str(n)))) }

Crossrefs

Sequence in context: A230199 A275542 A187559 * A139751 A076779 A337008

Adjacent sequences: A104209 A104210 A104211 * A104213 A104214 A104215

Keyword

easy,nonn,base,look

Author

Cino Hilliard, Mar 13 2005

Status

approved