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A182647 a(n) = the largest n-digit number with exactly 5 divisors, a(n) = 0 if no such number exists. 3
0, 81, 625, 2401, 83521, 923521, 7890481, 88529281, 895745041, 9597924961, 96254442001, 988053892081, 9971252437441, 96840734511361, 999706081460641, 9892436613211441, 99510671548640641, 998005893107997601 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = the largest n-digit number of the form p^4  (p = prime), a(n) = 0 if no such number exists.

LINKS

Table of n, a(n) for n=1..18.

FORMULA

A000005(a(n)) = 5.

MAPLE

A182647 := proc(n) a := 0 ; for i from 1 do p := ithprime(i)^4 ; if A055642(p) > n then return a ; elif A055642(p) = n then a := p; end if; end do: end proc:

MATHEMATICA

Table[Prime[PrimePi[10^(n/4)]]^4, {n, 2, 50}]

CROSSREFS

Cf. A030514, A174336.

Sequence in context: A235432 A206064 A016756 * A256590 A322240 A185856

Adjacent sequences:  A182644 A182645 A182646 * A182648 A182649 A182650

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Nov 27 2010

EXTENSIONS

Mathematica program by Zak Seidov, Nov 27 2010

STATUS

approved

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Last modified November 26 10:43 EST 2022. Contains 358356 sequences. (Running on oeis4.)