A113889 Smallest prime of the form: all sevens followed by prime(n); a(n) > prime(n); or 0 if no such prime exists.

0, 73, 0, 0, 77711, 77713, 7717, 719, 7723, 77777777777777777729, 77731, 777737, 7741, 743, 77747, 7753, 7759, 761, 77777777767, 7777777777771, 773, 777777777777777777777777777777777777777777777777777777777777777779

Offset: 1

Author

Amarnath Murthy, Nov 18 2005

Keywords

• base
• nonn

Comments

Prime(n) is all zeros followed by prime(n).This is all sevens followed by prime(n). Conjecture: a(n) is nonzero if n >4.

The conjecture has been verified for n<100. - Joshua Albert (jba138(AT)psu.edu), Jan 20 2006

Examples

			a(9) = 7723, as 723 is composite, prime(9) = 23.
		

Crossrefs

Cf. A113884, A114785, A113886, A113887, A085074.

Programs

Mathematica

Join[{0,73,0,0},Flatten[Select[#,PrimeQ,1]&/@Table[FromDigits[ PadLeft[ IntegerDigits[n],i,7]],{n,Prime[Range[5,30]]},{i,IntegerLength[ n]+1, 100}]]] (* Harvey P. Dale, Nov 20 2013 *)

Extensions

More terms from Joshua Albert (jba138(AT)psu.edu), Jan 20 2006