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 A268145 Twin prime pairs concatenated to their average in decimal representation (with the lesser twin prepended and the greater twin appended). 1
 345, 567, 111213, 171819, 293031, 414243, 596061, 717273, 101102103, 107108109, 137138139, 149150151, 179180181, 191192193, 197198199, 227228229, 239240241, 269270271, 281282283, 311312313, 347348349, 419420421, 431432433, 461462463, 521522523, 569570571, 599600601 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The lesser prime of a twin prime pair is prepended and the greater prime is appended to their average (nonprime, interprime). a(n) mod 3 = 0, (See A095958). LINKS Table of n, a(n) for n=1..27. EXAMPLE a(1)=345: the lesser prime {3} of the first twin prime pair {3, 5} is prepended and the greater prime {5} is appended to their average {4}. a(3)=111213: the lesser {11} of the 3rd twin prime pair {11, 13} is prepended and the greater prime {13} is appended to their average {12}. MATHEMATICA UpToN[k_]:=FromDigits//@ StringJoin//@ ToString/@ {#-1, #, #+1} &/@ Select[ Table[ Prime[n]+1, {n, 2, PrimePi[k]}], PrimeQ[#+1] &]; UpToN[10000] CROSSREFS Cf. A001097, A014574, A095958, A111875. Sequence in context: A251819 A251812 A251811 * A116347 A063370 A095963 Adjacent sequences: A268142 A268143 A268144 * A268146 A268147 A268148 KEYWORD nonn,base,easy AUTHOR Mikk Heidemaa, Jan 27 2016 STATUS approved

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Last modified August 9 14:35 EDT 2024. Contains 375042 sequences. (Running on oeis4.)