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 A173914 Primes of the form R(n!-1), where R is the digit reversal. 2

%I

%S 5,911,999138804001546121

%N Primes of the form R(n!-1), where R is the digit reversal.

%C The next term is too large to include.

%C Values of n are 3, 5, 19, 254, 266, ... [_Charles R Greathouse IV_, Feb 15 2011]

%C The next term (a(4)) has 503 digits. - _Harvey P. Dale_, Jan 17 2023

%e n=5 -> 5!-1 = 120-1=119 -> R(119)=911 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[IntegerReverse/@(Range[20]!-1),PrimeQ] (* _Harvey P. Dale_, Jan 17 2023 *)

%Y Cf. A173913, A173915, A173916.

%K nonn,bref,base

%O 1,1

%A _Paolo P. Lava_ and _Giorgio Balzarotti_, Mar 02 2010

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Last modified March 30 05:16 EDT 2023. Contains 361606 sequences. (Running on oeis4.)