A071263 Smallest nontrivial composite number beginning with n.

12, 21, 32, 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

Offset

1,1

Comments

Nontrivial means that simply appending a 0 to n is not allowed, nor is n itself.

Links

Table of n, a(n) for n=1..53.

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

a(3) corrected by Sean A. Irvine, Jul 06 2024

Status

approved