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%I #7 Jul 25 2015 01:29:22
%S 1,1,3,11,1,3,3,53,13,39,9,3,21,53,79,11,19,59,27,49,21,23,211,153,
%T 189,3,161,121,167,183,193,77,21,349,107,129,343,119,241,143,37,77,31,
%U 159,183,531,1517,7,59,159,123,9,1513,203,343,59,9,999,813,421,209,517,3
%N a(1) = 1; a(n) = smallest number such that the juxtaposition a(1)a(2)...a(n) is a prime.
%e The first few terms are 1,1,3,11,1,3,3,53,13,39,9,3. The next integer you can concatenate to the end of this to get a prime is 21 so the next term is 21. If you require terms to have all digits odd you would get 399 instead, giving A069604.
%t nn[a_] := For[b = 1, ! PrimeQ[n], b = b + 1, n = a*10^Floor[Log[10, b] + 1]] (* o get the next number in the sequence if a is the concatenation of all previous. *) nnt[m_] := (t = 1; Table[c = nnn[t]; t = c[[2]]; c[[1]], {m}]) (* To get a table of the first n terms, ignoring a(1)=1*)
%t a[1] = 1; a[n_] := a[n] = Block[{k = 1, c = IntegerDigits @ Table[ a[i], {i, n - 1}]}, While[ !PrimeQ[ FromDigits @ Flatten @ Append[c, IntegerDigits[k]]], k += 2]; k]; Table[ a[n], {n, 63}] (* _Robert G. Wilson v_, Aug 05 2005 *)
%Y Cf. A033680, A074336, A069602, A069604, A069603, A069605, A069606, A069607, A069608, A069609, A069610, A069611, A111525.
%K base,nonn
%O 1,3
%A Christer Mauritz Blomqvist (MauritzTortoise(AT)hotmail.com), Apr 08 2004
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