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A084126 Prime factor <= other prime factor of n-th semiprime. 37
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
COMMENTS
Lesser of the prime factors of A001358(n). - Jianing Song, Aug 05 2022
LINKS
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. A001358 (the semiprimes), A084127 (greater of the prime factors of the semiprimes).
Sequence in context: A273458 A159953 A074595 * A136032 A135975 A334796
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, May 15 2003
STATUS
approved

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Last modified February 21 04:30 EST 2024. Contains 370219 sequences. (Running on oeis4.)