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A098450 Largest n-digit semiprime. 4
9, 95, 998, 9998, 99998, 999997, 9999998, 99999997, 999999991, 9999999997, 99999999997, 999999999997, 9999999999989, 99999999999997, 999999999999998, 9999999999999994, 99999999999999989, 999999999999999993 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

MATHEMATICA

NextSemiPrime[n_, k_: 1] := Block[{c = 0, sgn = Sign[k]}, sp = n + sgn; While[c < Abs[k], While[ PrimeOmega[sp] != 2, If[sgn < 0, sp--, sp++]]; If[sgn < 0, sp--, sp++]; c++]; sp + If[sgn < 0, 1, -1]]; f[n_] := NextSemiPrime[10^n, -1]; Array[f, 18] (* Robert G. Wilson v, Dec 18 2012 *)

CROSSREFS

Cf. A098449 (smallest n-digit semiprime), A003618 (largest n-digit prime), A001358 (semiprimes).

Sequence in context: A000562 A193216 A213019 * A065456 A052389 A197665

Adjacent sequences:  A098447 A098448 A098449 * A098451 A098452 A098453

KEYWORD

base,nonn

AUTHOR

Rick L. Shepherd, Sep 07 2004

STATUS

approved

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Last modified December 18 10:38 EST 2014. Contains 252154 sequences.