A182681 - OEIS

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A182681

a(n) is the smallest n-digit number with exactly 11 divisors, a(n) = 0 if no such number exists.

0, 0, 0, 1024, 59049, 0, 9765625, 0, 282475249, 0, 25937424601, 137858491849, 2015993900449, 41426511213649, 420707233300201, 4808584372417849, 13422659310152401, 174887470365513049, 1822837804551761449, 15516041187205853449, 110462212541120451001, 1091533853073393531649

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,4

COMMENTS

a(n) is the smallest n-digit number of the form p^10 (p = prime), a(n) = 0 if no such number exists.

LINKS

Table of n, a(n) for n=1..22.

FORMULA

A000005(a(n)) = 11.

a(n) = min { 0 } union ( A030629 intersect [10^(n-1), 10^n-1] )

PROG

(PARI) a(n)=(10^n>n=nextprime(sqrtn(10^(n-1), 10))^10)*n \\ M. F. Hasler, Nov 27 2010