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A329887
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a(0) = 1, a(1) = 2; for n > 1, if n is even, then a(n) = 2*a(n/2), and if n is odd, a(n) = A283980(a((n-1)/2)).
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4
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1, 2, 4, 6, 8, 36, 12, 30, 16, 216, 72, 900, 24, 180, 60, 210, 32, 1296, 432, 27000, 144, 5400, 1800, 44100, 48, 1080, 360, 6300, 120, 1260, 420, 2310, 64, 7776, 2592, 810000, 864, 162000, 54000, 9261000, 288, 32400, 10800, 1323000, 3600, 264600, 88200, 5336100, 96, 6480, 2160, 189000, 720, 37800, 12600, 485100, 240
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OFFSET
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0,2
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LINKS
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FORMULA
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a(0) = 1, a(1) = 2; for n > 1, if n is odd, a(n) = A283980(a((n-1)/2)), and if n is even, then a(n) = 2*a(n/2).
a(2^n) = 2^(1+n). [And all the terms following after a(2^n) are > 2^(1+n).]
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EXAMPLE
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This irregular table can be represented as a binary tree. Each child to the left is obtained by doubling the parent, and each child to the right is obtained by applying A283980 to the parent:
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...................2...................
4 6
8......../ \........36 12......../ \........30
/ \ / \ / \ / \
/ \ / \ / \ / \
/ \ / \ / \ / \
16 216 72 900 24 180 60 210
etc.
A329886 is the mirror image of the same tree.
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MATHEMATICA
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{1}~Join~Nest[Append[#1, If[EvenQ@ #2, 2 #1[[#2/2]], (Times @@ Map[#1^#2 & @@ # &, FactorInteger[#] /. {p_, e_} /; e > 0 :> {Prime[PrimePi@ p + 1], e}] - Boole[# == 1])*2^IntegerExponent[#, 2] &[#1[[(#2 - 1)/2]] ]]] & @@ {#, Length@ # + 1} &, {2}, 55] (* Michael De Vlieger, Dec 29 2019 *)
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PROG
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(PARI)
A283980(n) = {my(f=factor(n)); prod(i=1, #f~, my(p=f[i, 1], e=f[i, 2]); if(p==2, 6, nextprime(p+1))^e)}; \\ From A283980
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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