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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

Table of n, a(n) for n=1..15.

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.)