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A143703 a(n) = A143702(n)/2. 3
3, 7, 15, 15, 21, 15, 39, 91, 555, 285, 915, 3333, 1155, 1267, 2769, 4935, 10005, 70635, 7035, 240045, 77745, 167055, 897429, 1231635, 1066065, 1174695 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The product of distinct prime divisors of (2^n)*a(n)*(2^n-a(n)) is also called the radical of that number: rad((2^n)*a(n)*(2^n-a(n))

For numbers a(n) see A143700.

For numbers 2^n-a(n) see A143701.

For minimal values of rad((2^n)*a(n)*(2^n-a(n)) see A143702.

For minimal values of rad(a(n)*(2^n-a(n)) see A143703. [? wrong A-number - N. J. A. Sloane, Nov 13 2008]

LINKS

Table of n, a(n) for n=1..26.

MATHEMATICA

a = {{1, 1}}; aa = {1}; bb = {1}; rr = {}; Do[logmax = 0; k = 2^x; w = Floor[(k - 1)/2]; Do[m = FactorInteger[n (k - n)]; rad = 1; Do[rad = rad m[[s]][[1]], {s, 1, Length[m]}]; log = Log[k]/Log[rad]; If[log > logmax, bmin = k - n; amax = n; logmax = log; r = rad], {n, 1, w, 2}]; Print[{x, amax}]; AppendTo[aa, amax]; AppendTo[bb, bmin]; AppendTo[rr, r]; AppendTo[a, {x, logmax}], {x, 2, 15}]; rr/2 (* Artur Jasinski with assistance of M. F. Hasler *)

CROSSREFS

Cf. A007947, A085152, A085153, A147298-A147307, A147638-A147643.

Sequence in context: A253582 A117589 A295930 * A098582 A235698 A089432

Adjacent sequences:  A143700 A143701 A143702 * A143704 A143705 A143706

KEYWORD

nonn,more

AUTHOR

Artur Jasinski, Nov 10 2008

STATUS

approved

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Last modified January 20 11:11 EST 2020. Contains 331083 sequences. (Running on oeis4.)