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A176316 Primes p with property that concatenation prime(1)//p//prime(2) = 2//p//3 is a prime.

%I A176316 #6 Nov 29 2017 23:02:25
%S A176316 2,3,11,29,47,59,71,83,101,131,149,167,227,257,317,347,359,383,389,
%T A176316 479,503,563,569,587,593,683,773,839,857,881,947,983,1019,1091,1109,
%U A176316 1187,1193,1229,1259,1319,1361,1499,1583,1613,1637,1697,1733,1823,1913,1931
%N A176316 Primes p with property that concatenation prime(1)//p//prime(2) = 2//p//3 is a prime.
%C A176316 Necessarily for p > 3: p = 6 * m + 5, as for q = 6*m+1 sod(2//q//3) is a multiple of 3
%D A176316 E. I. Ignatjew, Mathematische Spielereien, Urania Verlag Leipzig/Jena/Berlin 1982
%H A176316 Robert Israel, <a href="/A176316/b176316.txt">Table of n, a(n) for n = 1..10000</a>
%e A176316 223 = prime(48), 2 = prime(1) is first term
%e A176316 233 = prime(51), 3 = prime(2) is 2nd term
%e A176316 2//05//3 = 2053 = prime(310), a "leading" zero is included, no term of sequence
%e A176316 2113 = prime(319), 11 = prime(5) is 3rd term
%p A176316 filter:= p -> isprime(p) and isprime(10*p+3+2*10^(2+ilog10(p))):
%p A176316 select(filter, [2,3,seq(i,i=5..2000,6)]); # _Robert Israel_, Nov 29 2017
%K A176316 base,nonn
%O A176316 1,1
%A A176316 Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Apr 15 2010