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Revision History for A182672

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a(n) = the largest n-digit number with exactly 6 divisors, a(n) = 0 if no such number exists.
(history; published version)

#8 by Russ Cox at Fri Mar 30 19:00:24 EDT 2012

AUTHOR

_Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), _, Nov 27 2010

Discussion

Fri Mar 30

19:00

OEIS Server: https://oeis.org/edit/global/299

#7 by Russ Cox at Fri Mar 30 17:22:57 EDT 2012

EXTENSIONS

Extended by _T. D. Noe (noe(AT)sspectra.com), _, Nov 29 2010

Discussion

Fri Mar 30

17:22

OEIS Server: https://oeis.org/edit/global/120

#6 by T. D. Noe at Mon Nov 29 02:14:22 EST 2010

STATUS

proposed

approved

#5 by T. D. Noe at Mon Nov 29 02:14:04 EST 2010

DATA

0, 99, 981, 9981, 99997, 999981, 9999988, 99999961, 999999981, 9999999908, 99999999964, 999999999927, 9999999999884, 99999999999932, 999999999999908, 9999999999999925, 99999999999999963, 999999999999999929, 9999999999999999999, 99999999999999999916

COMMENTS

a(n) = the largest n-digit number of the form p^5 or p^2*q^1, (p, q = distinct primes), a(n) = 0 if no such number exists.

MATHEMATICA

Table[k=10^n-1; While[k>10^(n-1) && DivisorSigma[0, k] != 6, k--]; If[k==10^(n-1), k=0]; k, {n, 20}]

CROSSREFS

See Cf. A182671 (n) - the smallest n-digit number with exactly 6 divisors).

EXTENSIONS

Extended by T. D. Noe (noe(AT)sspectra.com), Nov 29 2010

STATUS

approved

proposed

#4 by N. J. A. Sloane at Sat Nov 27 15:09:24 EST 2010

STATUS

proposed

approved

#3 by Alonso del Arte at Sat Nov 27 15:08:40 EST 2010

NAME

a(n) = the largest n-digit number with exactly 6 divisors, a(n) = 0 if no such number exists.

COMMENTS

a(n) = the largest n-digit number of the form p^5 or p^2*q^1, (p, q = primes), a(n) = 0 if no such number exists.

FORMULA

A000005(a(n)) = 6.

CROSSREFS

See A182671(n) - the smallest n-digit number with exactly 6 divisors.

KEYWORD

nonn,new,base

#2 by Jaroslav Krizek at Sat Nov 27 15:01:45 EST 2010

NAME

allocated for Jaroslav Krizek a(n) = the largest n-digit number with exactly 6 divisors, a(n) = 0 if no such number exists.

DATA

0, 99, 981, 9981, 99997, 999981, 9999988, 99999961, 999999981, 9999999908

OFFSET

1,2

COMMENTS

a(n) = the largest n-digit number of the form p^5 or p^2*q^1, (p, q = primes), a(n) = 0 if no such number exists.

FORMULA

A000005(a(n)) = 6.

CROSSREFS

See A182671(n) - the smallest n-digit number with exactly 6 divisors.

KEYWORD

allocated

nonn

AUTHOR

Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Nov 27 2010

STATUS

approved

proposed

#1 by Jaroslav Krizek at Sat Nov 27 14:55:28 EST 2010

NAME

allocated for Jaroslav Krizek

KEYWORD

allocated

STATUS

approved