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

5, 911, 999138804001546121

Offset

1,1

Comments

The next term is too large to include.

Values of n are 3, 5, 19, 254, 266, ... [Charles R Greathouse IV, Feb 15 2011]

The next term (a(4)) has 503 digits. - Harvey P. Dale, Jan 17 2023

Links

Table of n, a(n) for n=1..3.

Example

n=5 -> 5!-1 = 120-1=119 -> R(119)=911 that is prime

Maple

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);

Mathematica

Select[IntegerReverse/@(Range[20]!-1), PrimeQ] (* Harvey P. Dale, Jan 17 2023 *)

Crossrefs

Cf. A173913, A173915, A173916.

Sequence in context: A299726 A094630 A284637 * A015940 A093853 A195627

Adjacent sequences: A173911 A173912 A173913 * A173915 A173916 A173917

Keyword

nonn,bref,base

Author

Paolo P. Lava and Giorgio Balzarotti, Mar 02 2010

Status

approved