A236671 Start with 8; thereafter, primes obtained by concatenating to the end of previous term the next smallest number that will produce a prime.
8, 83, 839, 83911, 839117, 83911721, 8391172123, 83911721233, 839117212337, 83911721233729, 839117212337293, 83911721233729399, 839117212337293999, 83911721233729399993, 839117212337293999931, 83911721233729399993139
Offset: 1
Examples
a(1) = 8 by definition. a(2) is the next smallest prime beginning with 8, so a(2) = 83. a(3) is the next smallest prime beginning with 83, so a(3) = 839.
Programs
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Mathematica
smp[n_]:=Module[{k=1},While[!PrimeQ[n*10^IntegerLength[k]+k],k++];n 10^IntegerLength[k]+ k]; NestList[smp,8,15] (* Harvey P. Dale, Aug 10 2024 *) -
Python
import sympy from sympy import isprime def b(x): num = str(x) n = 1 while n < 10**3: new_num = str(x) + str(n) if isprime(int(new_num)): print(int(new_num)) x = new_num n = 1 else: n += 1 b(8)
Comments