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 A068951 Scan the primes, record digit-sum if it is itself prime. 1
 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 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("")); CROSSREFS Cf. A046704. Sequence in context: A007605 A077765 A078400 * A139752 A238191 A004088 Adjacent sequences:  A068948 A068949 A068950 * A068952 A068953 A068954 KEYWORD easy,nonn,base AUTHOR Francois Jooste (phukraut(AT)hotmail.com), Mar 10 2002 STATUS approved

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Last modified April 7 04:20 EDT 2020. Contains 333292 sequences. (Running on oeis4.)