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A152021
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Numbers a(n) are obtained by the direct application of sieve of Eratosthenes for A000695: retaining A000695(2)=4, we delete all multiples of 4, which are more than 4; retaining A000695(3)=5, we delete all multiples of 5, which are more than 5, etc.
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9
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4, 5, 17, 21, 69, 81, 257, 261, 277, 321, 337, 341, 1041, 1089, 1093, 1109, 1297, 1301, 1349, 1361, 4101, 4113, 4117, 4161, 4177, 4181, 4353, 4357, 4373, 4417, 4421, 5121, 5137, 5141, 5189, 5201, 5377, 5381, 5393, 5441, 5461, 16389, 16449, 16453, 16469, 16641
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OFFSET
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1,1
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COMMENTS
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If p is prime, then A000695(p) is in the sequence; but, e. g., A000695(25), A000695(55) are also in the sequence.
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LINKS
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MAPLE
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A000695 := proc(n) local dgsa ; if n= 0 then 0; else for a from procname(n-1)+1 do dgsa := convert(convert(a, base, 4), set) ; if dgsa minus {0, 1} = {} then return a; end if; end do: end if; end proc:
A152021 := proc(nmax) a := [seq(A000695(i), i=2..nmax)] ; ptr := 1; while ptr < nops(a) do for j from nops(a) to ptr+1 by -1 do if op(j, a) mod op(ptr, a) = 0 then a := subsop(j=NULL, a) ; end if; end do: ptr := ptr+1 ; end do: a ; end proc: A152021(120) ; (End)
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MATHEMATICA
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f[n_] := FromDigits[IntegerDigits[n, 2], 4]; s = Array[f, 150, 2]; div[a_, b_] := Divisible[a, b] && a > b; n = 1; While[Length[s] > n, s = Select[s, !div[#, s[[n]]] &]; n++]; s (* Amiram Eldar, Aug 31 2019 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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