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A126289 a(1) = 1, a(2) = 1, a(n) = n * LargestPrimeFactor(n-1) / LargestPrimeFactor(n). 5
1, 1, 2, 6, 2, 10, 3, 28, 6, 6, 5, 44, 3, 26, 21, 40, 2, 102, 3, 76, 15, 14, 11, 184, 15, 10, 117, 12, 7, 174, 5, 496, 6, 22, 85, 84, 3, 74, 57, 104, 5, 246, 7, 172, 99, 10, 23, 752, 21, 70, 15, 68, 13, 954, 15, 88, 21, 38, 29, 708, 5, 122, 279, 224, 10, 78, 11, 268, 51, 230, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
LINKS
FORMULA
a(n) = A006530(n-1)*A052126(n) for n>2. - Michel Marcus, May 20 2015
EXAMPLE
a(6) = 6 * LargestPrimeFactor(5) / LargestPrimeFactor(6) = 6 * 5 / 3 = 10
MATHEMATICA
a[1] := 1; a[2] := 1; a[n_] := n*FactorInteger[n - 1][[-1, 1]]/FactorInteger[n][[-1, 1]]; Table[a[n], {n, 71}] (* Ivan Neretin, May 20 2015 *)
PROG
(PARI) gpf(n) = vecmax(factor(n)[, 1]); \\ A006530
a(n) = if (n<=2, 1, n*gpf(n-1)/gpf(n)); \\ Michel Marcus, Oct 07 2020
CROSSREFS
Sequence in context: A199154 A267859 A002172 * A200044 A154382 A136762
KEYWORD
easy,nonn
AUTHOR
Lior Manor, Dec 25 2006
STATUS
approved

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Last modified March 28 17:25 EDT 2024. Contains 371254 sequences. (Running on oeis4.)