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%I #17 Jul 12 2019 20:09:55
%S 2,23,223,2237,32237,3223729,63223729,632237297,2632237297,
%T 263223729721,12263223729721,1226322372972173,171226322372972173,
%U 17122632237297217381,2117122632237297217381,21171226322372972173813
%N a(1) = 2; a(2n) = smallest prime starting (the most significant digits) with a(2n-1) (i.e., as a right concatenation of a(2n-1) and a number with no insignificant zeros); a(2n+1) = smallest prime ending in (the least significant digits) a(2n-1). Alternate left and right concatenation yielding primes.
%e a(4) = 2111 staring with a(3) = 211 and a(5) = 22111 ending in a(4) = 2111.
%Y Cf. A053582, A069605, A069606, A069607, A069608, A069609, A069610, A069611, A069613.
%K nonn,base
%O 1,1
%A _Amarnath Murthy_, Mar 27 2002
%E More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 30 2003