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A084126 Prime factor <= other prime factor of n-th semiprime. 36
2, 2, 3, 2, 2, 3, 3, 2, 5, 2, 3, 2, 5, 2, 3, 2, 7, 3, 5, 3, 2, 2, 5, 3, 2, 7, 2, 5, 2, 3, 7, 3, 2, 5, 2, 3, 5, 2, 7, 11, 2, 3, 3, 7, 2, 3, 2, 11, 5, 2, 5, 2, 3, 7, 2, 13, 3, 2, 3, 5, 11, 2, 3, 2, 7, 5, 2, 11, 3, 2, 5, 7, 2, 3, 13, 2, 5, 3, 13, 3, 11, 2, 7, 2, 5, 3, 2, 2, 7, 17, 3, 5, 2, 13, 7, 2, 3, 5, 3, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Semiprime

FORMULA

a(n) = A020639(A001358(n)).

a(n) = A001358(n)/A006530(A001358(n)). [corrected by Michel Marcus, Jul 18 2020]

a(n) = A001358(n)/A084127(n).

MATHEMATICA

FactorInteger[#][[1, 1]]&/@Select[Range[500], PrimeOmega[#]==2&] (* Harvey P. Dale, Jun 25 2018 *)

PROG

(Haskell)

a084126 = a020639 . a001358  -- Reinhard Zumkeller, Nov 25 2012

CROSSREFS

Cf. A068318, A087718, A087794, A089994, A089995, A096916, A106550, A106554, A108541, A131284, A138510, A138511.

Sequence in context: A273458 A159953 A074595 * A136032 A135975 A334796

Adjacent sequences:  A084123 A084124 A084125 * A084127 A084128 A084129

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, May 15 2003

STATUS

approved

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Last modified April 10 22:27 EDT 2021. Contains 342856 sequences. (Running on oeis4.)