A176316 - OEIS

%I #6 Nov 29 2017 23:02:25

%S 2,3,11,29,47,59,71,83,101,131,149,167,227,257,317,347,359,383,389,

%T 479,503,563,569,587,593,683,773,839,857,881,947,983,1019,1091,1109,

%U 1187,1193,1229,1259,1319,1361,1499,1583,1613,1637,1697,1733,1823,1913,1931

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

%C Necessarily for p > 3: p = 6 * m + 5, as for q = 6*m+1 sod(2//q//3) is a multiple of 3

%D E. I. Ignatjew, Mathematische Spielereien, Urania Verlag Leipzig/Jena/Berlin 1982

%H Robert Israel, <a href="/A176316/b176316.txt">Table of n, a(n) for n = 1..10000</a>

%e 223 = prime(48), 2 = prime(1) is first term

%e 233 = prime(51), 3 = prime(2) is 2nd term

%e 2//05//3 = 2053 = prime(310), a "leading" zero is included, no term of sequence

%e 2113 = prime(319), 11 = prime(5) is 3rd term

%p filter:= p -> isprime(p) and isprime(10*p+3+2*10^(2+ilog10(p))):

%p select(filter, [2,3,seq(i,i=5..2000,6)]); # _Robert Israel_, Nov 29 2017

%K base,nonn

%O 1,1

%A Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Apr 15 2010