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 A090266 Least k such that concatenation k, prime(n), k is a prime. 2
 7, 1, 1, 3, 13, 17, 1, 9, 1, 1, 3, 3, 3, 3, 1, 1, 3, 3, 3, 7, 3, 3, 1, 57, 17, 3, 3, 1, 9, 1, 33, 1, 19, 3, 1, 3, 3, 9, 57, 1, 3, 21, 7, 9, 1, 21, 9, 3, 7, 21, 7, 1, 3, 1, 3, 3, 3, 3, 9, 7, 3, 3, 3, 3, 9, 1, 9, 41, 7, 3, 3, 1, 29, 9, 11, 1, 3, 9, 1, 9, 7, 3, 3, 17, 9, 1, 31, 17, 3, 17, 3, 7, 27, 3, 9, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 MATHEMATICA lk[n_]:=Module[{idn=IntegerDigits[n], k=1}, While[!PrimeQ[FromDigits[ Join[ IntegerDigits[k], idn, IntegerDigits[k]]]], k=k+2]; k]; Table[lk[i], {i, Prime[ Range[100]]}] (* Harvey P. Dale, Apr 26 2015 *) CROSSREFS Cf. A090267. Sequence in context: A241299 A090269 A086867 * A010142 A294646 A051422 Adjacent sequences:  A090263 A090264 A090265 * A090267 A090268 A090269 KEYWORD base,nonn AUTHOR Amarnath Murthy, Nov 28 2003 EXTENSIONS More terms from David Wasserman, Oct 24 2005 STATUS approved

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Last modified January 23 01:37 EST 2021. Contains 340384 sequences. (Running on oeis4.)