A127891 Smallest n-digit left-truncatable prime.

2, 13, 113, 1223, 12113, 121283, 1237547, 12184967, 124536947, 1219861613, 12181833347, 121339693967, 1213536676883, 12673876537547, 121848768729173, 1275463876537547, 12429121339693967, 165678739293946997, 1276812967623946997, 15396334245663786197, 315396334245663786197, 5918918997653319693967, 57686312646216567629137, 357686312646216567629137

Offset: 1

Author

Ray Chandler, Feb 04 2007

Keywords

• base
• nonn
• fini
• full

Comments

Ends at a(24) = 357686312646216567629137.

Agrees with A088604 for 24 terms, but this sequence ends there while A088604 continues.

Links

• Ray Chandler, Table of n, a(n) for n = 1..24
• I. O. Angell and H. J. Godwin, On Truncatable Primes, Math. Comput. 31, 265-267, 1977.
• Index entries for sequences related to truncatable primes

Crossrefs

Cf. A024785, A050987, A088604, A127892.

Programs

Mathematica

grow[p_, digits_] := Select[ Table[ FromDigits[Join[{k}, IntegerDigits[p]]], {k, 1, 9}], PrimeQ[#] && Length[ IntegerDigits[#]] == digits&]; g[1] = {3, 7}; g[n_] := g[n] = grow[#, n]& /@ g[n-1] // Flatten; a[1] = 2; a[n_] := Min[g[n]]; Table[a[n], {n, 1, 24}] (* Jean-François Alcover, Aug 05 2013 *)