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%I #14 Oct 24 2020 17:23:12
%S 2,11,151,1013,10867,100673,1000357,10000931,100000213,1000000901,
%T 10000001797,100000000283,1000000001911,10000000012553,
%U 100000000006087,1000000000011317,10000000000003471,100000000000017431
%N a(n) is the smallest n-digit prime p such that the concatenation a(1)a(2)...a(n-1)p is prime, with a(1) = 2.
%C The corresponding primes are certified for 44 < n < 60 (for the first 15 titanic primes). - _Metin Sariyar_, Oct 23 2020
%H Metin Sariyar, <a href="/A049462/b049462.txt">Table of n, a(n) for n = 1..100</a>
%e Starting with an initial prime of 2, next the smallest 2-digit prime which gives a prime is 11 (211, a prime), then 151 (3-digit prime) is the smallest to make 211151 a prime, etc.
%t NextPrim[n_] := Block[{k = n + 1}, While[ ! PrimeQ[k], k++ ]; k]; a[1] = 2; a[n_] := a[n] = Block[{p = Sum[ a[i]*10^(n(n + 1)/2 - i(i + 1)/2), {i, 1, n - 1}], q = NextPrim[10^(n - 1)]}, While[ !PrimeQ[p + q], q = NextPrim[q]]; q]; Table[ a[n], {n, 1, 19}] (* _Robert G. Wilson v_, Oct 18 2003 *)
%Y Cf. A080155, A083758.
%K nonn,base
%O 1,1
%A _Jeff Heleen_, Oct 13 2003
%E More terms from _Robert G. Wilson v_, Oct 18 2003
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