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%I #5 Aug 24 2012 10:50:03
%S 2,7,41,383,401,449,9911985173,422341432613,9991380634172583438761,
%T 426098774309076039404423265983175582575572211,
%U 4260466555914046005704099160490768769763030425914059033564091456450512175875462052616893583
%N Primes of the form R(n!!-1), where R(k) is the digit reversal of k.
%e n=7 -> 7!!-1 = 105-1=104 -> R(104)=401 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:=doublefactorial(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);
%Y Cf. A173913-A173915
%K nonn,base
%O 1,1
%A _Paolo P. Lava_ and _Giorgio Balzarotti_, Mar 02 2010, Mar 05 2010
%E Edited by _Charles R Greathouse IV_, Aug 02 2010
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