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A216324 One half of the radical (squarefree kernel) of the abc-triples (a=1, b(n) = A216323(n), c(n) = 1 + b(n)). 2
3, 21, 21, 15, 105, 33, 51, 57, 195, 195, 273, 465, 205, 285, 987, 105, 1155, 897, 651, 1365, 105, 357, 1185, 615, 715, 665, 2345, 4395, 2037, 1155, 3003, 897, 1239, 3255, 2667, 8463, 5691, 7755, 2415, 4305, 11985, 4123 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See a comment on A216323 for the definition of an abc-triple, radical r and quality q which is always > 1 by this definition. There also a link is given.

LINKS

Table of n, a(n) for n=1..42.

Wolfdieter Lang, Maple program for radical of a*b*(a+b) .

FORMULA

a(n) = r(1,b(n),b(n)+1) with b(n) = A216323(n), n>=1, and r(a,b,c) is the radical, also known as squarefree kernel, of a*b*c.

EXAMPLE

2*105 = 2*a(21) = r(1,4374,4375) = 1*6*35 = 210.

MAPLE

read "radabc.txt": [seq(radabc(1, A216324(n)), n=1..42)]/2;

(with the above given link with the maple text file)

MATHEMATICA

rad[n_] := Times @@ Transpose[FactorInteger[n]][[1]]; a = 1; Table[t = {}; mx = 10^n; Do[c = a + b; If[c < mx && GCD[a, b] == 1 && Log[c] > Log[rad[a*b*c]], AppendTo[t, rad[b*c]/2]], {b, a, mx - a}], {n, 5}]; t (* T. D. Noe, Sep 24 2012 *)

CROSSREFS

Cf. A216323.

Sequence in context: A212996 A089999 A124397 * A226319 A279842 A043081

Adjacent sequences:  A216321 A216322 A216323 * A216325 A216326 A216327

KEYWORD

nonn

AUTHOR

Wolfdieter Lang, Sep 24 2012

STATUS

approved

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Last modified August 12 10:31 EDT 2020. Contains 336438 sequences. (Running on oeis4.)