OFFSET
1,2
LINKS
Makoto Kamada, Search for 70w27.
EXAMPLE
3 is in this sequence because 7*10^3 + 27 = 7027 is prime.
4 is not in the sequence because 7*10^4 + 27 = 70027 = 239 * 293.
Initial terms and associated primes:
a(1) = 1: 97;
a(2) = 2: 727;
a(3) = 3: 7027;
a(4) = 5: 700027, etc.
MATHEMATICA
Select[Range[0, 3000], PrimeQ[7 10^# + 27] &]
PROG
(Magma) [n: n in [1..800] | IsPrime(7*10^n+27)];
(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(7*10^n+27), print1(n, ", "))); \\ Altug Alkan, Jul 05 2016
(Python)
from sympy import isprime
def afind(limit, startk=0):
sevenpow10 = 7*10**startk
for k in range(startk, limit+1):
if isprime(sevenpow10 + 27):
print(k, end=", ")
k += 1
sevenpow10 *= 10
afind(500) # Michael S. Branicky, Dec 31 2021
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Jul 04 2016
EXTENSIONS
a(15)-a(16) from Michael S. Branicky, Dec 31 2021
a(17)-a(20) from Kamada data by Tyler Busby, Apr 14 2024
STATUS
approved