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 A103617 Concatenations of pairs of primes that differ by 10^9. 1
 71000000007, 971000000097, 1031000000103, 1811000000181, 2231000000223, 2411000000241, 2711000000271, 3491000000349, 4091000000409, 4331000000433, 4391000000439, 6071000000607, 6131000000613, 7871000000787, 8291000000829 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Integers in this sequence can never be prime, as they are all multiples of 3. They can be semiprimes, as is the case for Prime(42) concatenated with Prime(50847544) = 1811000000181 = 3 x 603666666727. LINKS FORMULA a(n) = Concatenate(P, P+1000000000) iff P prime and P+1000000000 prime. EXAMPLE 181 is prime, 181+10^9 = 1000000181 is prime, so their concatenation is an element of this sequence: 1811000000181. Coincidentally, prime(181)+10^9 = 1000001087 is also prime. CROSSREFS Cf. A000040, A001358, A023201, A100750, A103195, A103206, A104718, A104719, A103523, A103534, A103576. Sequence in context: A321284 A186095 A218397 * A213334 A211417 A287246 Adjacent sequences:  A103614 A103615 A103616 * A103618 A103619 A103620 KEYWORD base,easy,nonn AUTHOR Jonathan Vos Post, Mar 25 2005 STATUS approved

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Last modified September 23 03:04 EDT 2020. Contains 337291 sequences. (Running on oeis4.)