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 A175188 Smallest composite numbers of the form k*10^k + 1 0
 201, 40001, 500001, 6000001, 70000001, 800000001, 100000000001, 1100000000001, 12000000000001, 130000000000001, 1400000000000001, 15000000000000001, 160000000000000001, 1700000000000000001, 18000000000000000001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 844. LINKS M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy]. EXAMPLE for k=2, n=201 = 3*67, for k=4, n = 40001 = 13*17*181 MAPLE with(numtheory):for k from 1 to 100 do: n:=k*10^k +1:if type(n, prime) = false then print(n):else fi:od: CROSSREFS Cf composite numbers: A002808 A005381 Sequence in context: A061697 A305724 A167070 * A227152 A210166 A216376 Adjacent sequences:  A175185 A175186 A175187 * A175189 A175190 A175191 KEYWORD nonn AUTHOR Michel Lagneau, Mar 01 2010 STATUS approved

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Last modified May 16 08:07 EDT 2021. Contains 343940 sequences. (Running on oeis4.)