|
%I #7 Aug 24 2012 10:50:03
%S 2,3,7,127,10861993,1008634767031,100690824786553,100238804001546121,
%T 1000867067777270004211,
%U 1000000000002116896100279523601123039646103424220822837823578111551
%N Primes of the form R(n!+1), where R(k) is the digit reversal of k.
%C Next term (n=867) has 2173 digits.
%e n=6 -> 6!+1 = 720+1=721 -> Reverse_Digits(721)=127 that is prime
%p P:=proc(i) local a,b,k,n,v; v:=array(1..10000); for n from 1 by 1 to i do a:=1; k:=n!+1; while k>0 do v[a]:=k-(trunc(k/10)*10); k:=trunc(k/10); a:=a+1; od; k:=0; for b from a-1 by -1 to 1 do k:=k+v[b]*10^(a-1-b); od; if isprime(k) then print(k); fi; od; end: P(2000);
%t Select[FromDigits[Reverse[IntegerDigits[#]]]&/@(Range[150]!+1),PrimeQ] (* _Harvey P. Dale_, Jul 11 2012 *)
%Y Cf. A173914-A173916
%K nonn,base
%O 1,1
%A _Paolo P. Lava_ and _Giorgio Balzarotti_, Mar 02 2010
%E Edited by _Charles R Greathouse IV_, Aug 02 2010
| 