Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
proposed
approved
editing
proposed
Robert Israel, <a href="/A176316/b176316.txt">Table of n, a(n) for n = 1..10000</a>
filter:= p -> isprime(p) and isprime(10*p+3+2*10^(2+ilog10(p))):
select(filter, [2, 3, seq(i, i=5..2000, 6)]); # Robert Israel, Nov 29 2017
approved
editing
223 = prime(48), 2 = prime(1) is 1st first term
base,nonn,new
Primes p with property that concatenation prime(1)//p//prime(2) = 2//p//3 is a prime.
2, 3, 11, 29, 47, 59, 71, 83, 101, 131, 149, 167, 227, 257, 317, 347, 359, 383, 389, 479, 503, 563, 569, 587, 593, 683, 773, 839, 857, 881, 947, 983, 1019, 1091, 1109, 1187, 1193, 1229, 1259, 1319, 1361, 1499, 1583, 1613, 1637, 1697, 1733, 1823, 1913, 1931
1,1
Necessarily for p > 3: p = 6 * m + 5, as for q = 6*m+1 sod(2//q//3) is a multiple of 3
E. I. Ignatjew, Mathematische Spielereien, Urania Verlag Leipzig/Jena/Berlin 1982
223 = prime(48), 2 = prime(1) is 1st term
233 = prime(51), 3 = prime(2) is 2nd term
2//05//3 = 2053 = prime(310), a "leading" zero is included, no term of sequence
2113 = prime(319), 11 = prime(5) is 3rd term
base,nonn
Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Apr 15 2010
approved