A068951 - OEIS

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A068951

Scan the primes, record digit-sum if it is itself prime.

2, 3, 5, 7, 2, 5, 11, 5, 7, 11, 7, 13, 11, 17, 2, 5, 5, 11, 13, 7, 13, 11, 17, 11, 13, 17, 19, 7, 11, 13, 7, 11, 17, 11, 13, 5, 7, 11, 7, 13, 11, 17, 13, 19, 19, 5, 13, 7, 11, 17, 11, 13, 17, 19, 17, 13, 19, 17, 23, 7, 13, 11, 13, 17, 13, 17, 17, 13, 19, 13, 19, 17, 23, 17, 11, 13

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..76.

EXAMPLE

a(13)=5 since the 13th prime is 41 and 4+1=5, which is prime.

MAPLE

dig := X->convert((convert(X, base, 10)), `+`); a := n->`if`(isprime(dig(ithprime(n)))=true, dig(ithprime(n)), printf(""));

MATHEMATICA

Select[Total[IntegerDigits[#]]&/@Prime[Range[200]], PrimeQ] (* Harvey P. Dale, Oct 17 2020 *)

CROSSREFS