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 A071263 Smallest nontrivial composite number beginning with n. 1
 12, 21, 33, 42, 51, 62, 72, 81, 91, 102, 111, 121, 132, 141, 152, 161, 171, 182, 192, 201, 212, 221, 231, 242, 252, 261, 272, 282, 291, 301, 312, 321, 332, 341, 351, 361, 371, 381, 391, 402, 411, 422, 432, 441, 451, 462, 471, 481, 492, 501, 511, 522, 531 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Nontrivial means that simply appending a 0 to n is not allowed, nor is n itself. LINKS MATHEMATICA a[n_] := (j = ToString[n]; l = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "01", "02", "03", "04", "05", "06", "07", "08", "09"}; k = 1; While[c = ToExpression[ StringJoin[j, ToString[ l[[k]] ]]]; k < 19 && PrimeQ[c], k++ ]; If[k < 19, Return[c]]; i = IntegerDigits[n]; k = 10; While[c = FromDigits[ Join[i, IntegerDigits[k]]]; PrimeQ[c], k++ ]; Return[c]); Table[ a[n], {n, 1, 55}] CROSSREFS Cf. A071262. Sequence in context: A316266 A179899 A085926 * A241503 A226186 A325301 Adjacent sequences:  A071260 A071261 A071262 * A071264 A071265 A071266 KEYWORD nonn,base,easy AUTHOR Amarnath Murthy, May 30 2002 EXTENSIONS Edited by Robert G. Wilson v, Jun 14 2002 STATUS approved

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Last modified January 19 16:16 EST 2021. Contains 340270 sequences. (Running on oeis4.)