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A215567 Numbers n with property that n and the n-th number which is a product of n primes have the largest prime divisor and with the same multiplicity. 0
3, 13, 20, 42, 44, 45, 56, 60, 86, 87, 112, 119, 121 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

a(2) = 13 because n = 13 and 13th 13-almost prime = 13*2^12 = 53248 has same largest prime factor = 13.

MATHEMATICA

AlmostPrimePi[k_Integer, n_]:=...; AlmostPrime[k_, n_]:=...;

fQ[n_]:=FactorInteger[n][[-1, 1]]==FactorInteger[AlmostPrime[n, n]][[-1, 1]]; k=1; lst={};

While[k<150, If[fQ@k, AppendTo[lst, k]; Print@k]; k++]; lst  (* Robert G. Wilson v, Aug 27 2012 *)

CROSSREFS

Cf. A001222, A101695, A215405.

Sequence in context: A271924 A178712 A273686 * A214519 A099502 A145024

Adjacent sequences:  A215564 A215565 A215566 * A215568 A215569 A215570

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Aug 16 2012

EXTENSIONS

a(9)-a(13) from Robert G. Wilson v, Aug 27 2012

Definition clarified by N. J. A. Sloane, Sep 04 2012

STATUS

approved

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Last modified June 20 17:43 EDT 2021. Contains 345199 sequences. (Running on oeis4.)