A114756 Smallest prime of the form: n successive positive integers in ascending order followed by a 7.

17, 127, 1237, 12347, 123457, 56789107, 456789107, 3456789107, 4567891011127, 616263646566676869707, 13141516171819202122237, 2021222324252627282930317, 151617181920212223242526277

Offset: 1

Author

Amarnath Murthy, Jan 01 2006

Keywords

• base
• nonn

Examples

			a(4) = 12347, four successive positive integers 1,2,3,4 in ascending order followed by a 7.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..40

Crossrefs

Cf. A114754, A114755, A114757, A114758, A114759, A112716, A108145.

Programs

Mathematica

a[n_]:=(For[m=1, (v={};Do[v=Join[v, IntegerDigits[k]], {k, m, m+n-1}]);!PrimeQ[10FromDigits[v]+7], m++ ];10FromDigits[v]+7);Table[a[n], {n, 14}] - Farideh Firoozbakht
f[n_] := Block[{t = Range@n}, While[p = FromDigits@Flatten@IntegerDigits@Join[t, {7}]; !PrimeQ@p, t++ ]; p]; Array[f, 14] (* Robert G. Wilson v *)
Table[SelectFirst[10 FromDigits[Flatten[IntegerDigits/@#]]+7&/@ Partition[ Range[1000],n,1],PrimeQ],{n,20}] (* Harvey P. Dale, Jan 29 2022 *)

Extensions

Extended by Robert G. Wilson v, Ray Chandler and Farideh Firoozbakht, Jan 02 2006