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A069636 a(1) = 9; a(2n) = smallest prime starting (most significant digits) with a(2n-1). a(2n+1) = smallest prime ending (least significant digits)in a(2n).

%I A069636 #6 Nov 11 2020 22:50:13
%S A069636 9,97,197,1973,31973,319733,3319733,331973303,5331973303,533197330313,
%T A069636 9533197330313,953319733031321,3953319733031321,395331973303132171,
%U A069636 12395331973303132171,1239533197330313217121,391239533197330313217121
%N A069636 a(1) = 9; a(2n) = smallest prime starting (most significant digits) with a(2n-1). a(2n+1) = smallest prime ending (least significant digits)in a(2n).
%H A069636 Robert Israel, <a href="/A069636/b069636.txt">Table of n, a(n) for n = 1..348</a>
%p A069636 A[1]:= 9:
%p A069636 for n from 2 to 30 do
%p A069636   if n::even then
%p A069636     for d from 1 do
%p A069636       x:= nextprime(A[n-1]*10^d);
%p A069636       if x < (A[n-1]+1)*10^d then A[n]:= x; break fi
%p A069636     od
%p A069636   else
%p A069636     d:=ilog10(A[n-1])+1;
%p A069636     for x from A[n-1]+10^d by 10^d do
%p A069636       if isprime(x) then A[n]:= x; break fi
%p A069636     od
%p A069636   fi
%p A069636 od:
%p A069636 seq(A[i],i=1..30); # _Robert Israel_, Nov 11 2020
%Y A069636 Cf. A069614 to A069621, A069628 to A069636.
%K A069636 nonn,base
%O A069636 1,1
%A A069636 _Amarnath Murthy_, Mar 27 2002
%E A069636 Edited and extended by _Robert G. Wilson v_, Apr 03 2002