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A152021
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.
9
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
OFFSET
1,1
COMMENTS
If p is prime, then A000695(p) is in the sequence; but, e. g., A000695(25), A000695(55) are also in the sequence.
MAPLE
Contribution from R. J. Mathar, Oct 29 2010: (Start)
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)
MATHEMATICA
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 *)
CROSSREFS
Cf. A000695.
Sequence in context: A344061 A045680 A174352 * A026678 A026869 A350662
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Nov 20 2008
EXTENSIONS
More terms from R. J. Mathar, Oct 29 2010
More terms from Amiram Eldar, Aug 31 2019
STATUS
approved