OFFSET
1,1
COMMENTS
Subsequence of A046704; actually, exactly those numbers for which the orbit under A007953 is a subset of A046704. - M. F. Hasler, Jun 28 2009
Supersequences: A046704 is primes p with digit sum s(p) also prime; A207294 is primes p with s(p) and s(s(p)) also prime.
Disjoint sequences: A104213 is primes p with s(p) not prime; A207293 is primes p with s(p) also prime, but not s(s(p)); A213354 is primes p with s(p) and s(s(p)) also prime, but not s(s(s(p))); A213355 is smallest prime p with k-fold digit sum s(s(..s(p)).)..)) also prime for all k < n, but not for k = n. - Jonathan Sondow, Jun 13 2012
LINKS
Alex Costea, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Alois P. Heinz)
Glyn Harman, Counting Primes whose Sum of Digits is Prime, J. Integer Seq., 15 (2012), Article 12.2.2.
EXAMPLE
MATHEMATICA
dspQ[n_] := TrueQ[Union[PrimeQ[NestWhileList[Plus@@IntegerDigits[#] &, n, # > 9 &]]] == {True}]; Select[Prime[Range[200]], dspQ] (* Alonso del Arte, Aug 17 2011 *)
isdpQ[n_]:=AllTrue[Rest[NestWhileList[Total[IntegerDigits[#]]&, n, #>9&]], PrimeQ]; Select[Prime[Range[300]], isdpQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jul 12 2017 *)
PROG
(PARI) isA070027(n)={ while(isprime(n), n<9 && return(1); n=vector(#n=eval(Vec(Str(n))), i, 1)*n~)} \\ M. F. Hasler, Jun 28 2009
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Rick L. Shepherd, Apr 14 2002
STATUS
approved