This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A181576 #17 May 03 2024 04:18:15 %S A181576 11,13,17,19,31,59,83,127,151,173,179,197,199,223,293,367,397,421,439, %T A181576 449,461,463,557,569,607,617,619,631,659,733,773,797,853,919,941,967, %U A181576 1013,1039,1061,1063,1087,1097,1123,1181,1259,1399,1423,1447,1543,1567 %N A181576 Primes whose factorials end with a prime number of trailing 0's. %C A181576 For the corresponding prime number of trailing end 0's, see A181577. %H A181576 Amiram Eldar, <a href="/A181576/b181576.txt">Table of n, a(n) for n = 1..10000</a> %F A181576 A027868(a(n)) = A181577(n). - _Amiram Eldar_, May 03 2024 %e A181576 The factorial 2! = 2 ends with 0 zeros, so the prime 2 is not in the sequence because 0 is not a prime. %e A181576 The factorial 5! = 120 ends with 1 zero, so the prime 5 is not in the sequence because 1 is not a prime. %e A181576 The factorial 11! = 39916800 ends with 2 zeros, so the prime 11 is in the sequence because 2 is a prime. %t A181576 Select[ Prime@ Range@ 250, PrimeQ@ IntegerExponent[ #! ] &] (* _Robert G. Wilson v_, Nov 06 2010 *) %o A181576 (PARI) is(p) = isprime(p) && isprime((p - sumdigits(p, 5))/4); \\ _Amiram Eldar_, May 03 2024 %Y A181576 Cf. A027868, A039716, A181577. %K A181576 nonn,base %O A181576 1,1 %A A181576 _Lekraj Beedassy_, Nov 02 2010 %E A181576 More terms from _Robert G. Wilson v_, Nov 06 2010