|
%I #8 Apr 17 2013 18:04:53
%S 3,6,10,14,15,24,30,33,34,39,40,47,53,57,61,71,75,76,80,81,83,88,89,
%T 92,102,103,106,117,131,143,144,147,154,163,170,187,198,200,205,210,
%U 212,221,227,238,240,253,255,260,262,265,271,275
%N Numbers n such that the sum of the digits of 13^n is prime.
%H Vincenzo Librandi, <a href="/A134535/b134535.txt">Table of n, a(n) for n = 1..1000</a>
%e 13^3=2197 and 2+1+9+7=19 is prime.
%p P:=proc(n) local cont,i,k,w; if isprime(n) then cont:=0; while cont<1000 do cont:=cont+1; w:=0; k:=n^cont; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if isprime(w) then print(cont); fi; od; fi; end: P(13);
%t Select[Range[250], PrimeQ[Total[IntegerDigits[13^#]]]&] (* _Vincenzo Librandi_, Apr 17 2013 *)
%Y Cf. A076203, A134532, A134533, A134534.
%K easy,nonn,base
%O 1,1
%A _Paolo P. Lava_ and _Giorgio Balzarotti_, Oct 30 2007
|
