OFFSET
1,1
COMMENTS
With k>1 the number of entries is greatly reduced compared to simply allowing p+digsum(p) = q. One could allow for k=1 to see how many entries could be found for a variation of this sequence.
LINKS
Kevin P. Thompson, Table of n, a(n) for n = 1..1000 (first 181 terms from Michel Marcus)
EXAMPLE
a(4)=521 because 521+5+2+1=529=23^2 and 23 is a prime.
MATHEMATICA
a242368[n_Integer] := Module[{p, pp}, p = Prime[n]; pp = p + Plus @@ IntegerDigits@p; If[And[Length@FactorInteger[pp] == 1,
Min[Last@Transpose[FactorInteger[pp]]] > 1], p, 0]]; Rest@Sort@DeleteDuplicates[a242368 /@ Range[10^6]] (* Michael De Vlieger, Aug 16 2014 *)
PROG
(PARI) dsum(n)=n=digits(n); sum(i=1, #n, n[i])
is(p)=isprimepower(p+dsum(p))>1 && isprime(p)
forprime(p=2, 1e9, if(is(p), print1(p", "))) \\ Charles R Greathouse IV, Aug 16 2014
CROSSREFS
KEYWORD
nonn,base
AUTHOR
J. M. Bergot, Aug 16 2014
EXTENSIONS
More terms from Charles R Greathouse IV, Aug 16 2014
STATUS
approved