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A181576
Primes whose factorials end with a prime number of trailing 0's.
2
11, 13, 17, 19, 31, 59, 83, 127, 151, 173, 179, 197, 199, 223, 293, 367, 397, 421, 439, 449, 461, 463, 557, 569, 607, 617, 619, 631, 659, 733, 773, 797, 853, 919, 941, 967, 1013, 1039, 1061, 1063, 1087, 1097, 1123, 1181, 1259, 1399, 1423, 1447, 1543, 1567
OFFSET
1,1
COMMENTS
For the corresponding prime number of trailing end 0's, see A181577.
LINKS
FORMULA
A027868(a(n)) = A181577(n). - Amiram Eldar, May 03 2024
EXAMPLE
The factorial 2! = 2 ends with 0 zeros, so the prime 2 is not in the sequence because 0 is not a prime.
The factorial 5! = 120 ends with 1 zero, so the prime 5 is not in the sequence because 1 is not a prime.
The factorial 11! = 39916800 ends with 2 zeros, so the prime 11 is in the sequence because 2 is a prime.
MATHEMATICA
Select[ Prime@ Range@ 250, PrimeQ@ IntegerExponent[ #! ] &] (* Robert G. Wilson v, Nov 06 2010 *)
PROG
(PARI) is(p) = isprime(p) && isprime((p - sumdigits(p, 5))/4); \\ Amiram Eldar, May 03 2024
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Lekraj Beedassy, Nov 02 2010
EXTENSIONS
More terms from Robert G. Wilson v, Nov 06 2010
STATUS
approved