A053547 Smallest prime starting with A000422(n).

11, 211, 3217, 432121, 543217, 65432117, 76543217, 876543211, 9876543211, 1098765432101, 11109876543211, 12111098765432101, 1312111098765432139, 141312111098765432113, 15141312111098765432173

Offset: 1

Author

Enoch Haga, Jan 16 2000

Keywords

• easy
• nice
• nonn
• base

Examples

			a(6)=65432117 is smallest prime beginning with the string 654321.
		

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A000422.

Programs

Mathematica

Flatten[Select[Join[10 #+Range[1,9,2],100 #+Range[1,99,2]],PrimeQ,1]&/@ Table[FromDigits[Flatten[IntegerDigits/@Range[n,1,-1]]],{n,25}]] (* Harvey P. Dale, Nov 04 2011 *)

Python

from sympy import isprime
def A053547(n):
    s = int(''.join(str(m) for m in range(n,0,-1)))
    for i in range(1,10):
        s *= 10
        for j in range(1,10**i,2):
            x = s+j
            if isprime(x):
                return x
    else:
        return 'search limit reached.' # Chai Wah Wu, Jan 02 2015