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A182683 a(n) = the smallest n-digit number with exactly 12 divisors, a(n) = 0 if no such number exists. 1
0, 60, 108, 1012, 10004, 100004, 1000012, 10000025, 100000012, 1000000025, 10000000012, 100000000004, 1000000000017, 10000000000004, 100000000000012, 1000000000000004, 10000000000000025, 100000000000000004, 1000000000000000017, 10000000000000000034, 100000000000000000012, 1000000000000000000025, 10000000000000000000004, 100000000000000000000004 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = the smallest n-digit number of the form p^11, p^5*q, p^3*q^2 or p^2*q*r (p, q, r distinct primes), a(n) = 0 if no such number exists.

LINKS

Table of n, a(n) for n=1..24.

FORMULA

A000005(a(n)) = 12.

a(n) <= A182684(n).

MATHEMATICA

Table[k=10^(n-1); While[k<10^n && DivisorSigma[0, k] != 12, k++]; If[k==10^n, k=0]; k, {n, 20}]

CROSSREFS

Cf. A030630, A182684.

Sequence in context: A258700 A008887 A217738 * A174601 A306908 A252961

Adjacent sequences:  A182680 A182681 A182682 * A182684 A182685 A182686

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Nov 27 2010

STATUS

approved

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Last modified November 17 06:06 EST 2019. Contains 329217 sequences. (Running on oeis4.)