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 A322982 If n is a noncomposite, then a(n) = 2*n - 1, otherwise a(n) = A032742(n), the largest proper divisor of n. 2
 1, 3, 5, 2, 9, 3, 13, 4, 3, 5, 21, 6, 25, 7, 5, 8, 33, 9, 37, 10, 7, 11, 45, 12, 5, 13, 9, 14, 57, 15, 61, 16, 11, 17, 7, 18, 73, 19, 13, 20, 81, 21, 85, 22, 15, 23, 93, 24, 7, 25, 17, 26, 105, 27, 11, 28, 19, 29, 117, 30, 121, 31, 21, 32, 13, 33, 133, 34, 23, 35, 141, 36, 145, 37, 25, 38, 11, 39, 157, 40, 27, 41, 165, 42, 17, 43, 29 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Antti Karttunen, Table of n, a(n) for n = 1..20000 FORMULA If A010051(n) == 1, a(n) = 2*n - 1, otherwise a(n) = A032742(n) = n/A020639(n). MATHEMATICA Array[If[CompositeQ@ #, Divisors[#][[-2]], 2 # - 1] &, 87] (* Michael De Vlieger, Jan 03 2019 *) PROG (PARI) A322982(n) = if((1==n)||isprime(n), n+n-1, n/vecmin(factor(n)[, 1])); CROSSREFS Cf. A010051, A020639, A032742, A087717. Sequence in context: A075626 A152649 A186412 * A275846 A273668 A245653 Adjacent sequences:  A322979 A322980 A322981 * A322983 A322984 A322985 KEYWORD nonn AUTHOR Antti Karttunen, Jan 03 2019 STATUS approved

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Last modified March 25 01:17 EDT 2019. Contains 321450 sequences. (Running on oeis4.)