cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A152023 Numbers in A152022 which are not products of terms of A152021.

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%I A152023 #7 Sep 01 2019 02:36:48
%S A152023 65,260,273,325,1025,1029,1040,1045,1092,1105,1281,1300,1345,1365,
%T A152023 4097,4100,4116,4160,4165,4180,4368,4420,4433,5124,5125,5185,5200,
%U A152023 5380,5460,16385,16388,16400,16401,16405,16464,16465,16640,16645,16660,16705,16709,16720
%N A152023 Numbers in A152022 which are not products of terms of A152021.
%t A152023 f[n_] := FromDigits[IntegerDigits[n, 2], 4];  s = Array[f, 300, 2]; div[a_, b_] := Divisible[a, b] && a > b; n = 1; s0 = s; While[Length[s] > n, s = Select[s, ! div[#, s[[n]]] &]; n++]; s1 = Complement[s0, s]; aQ[n_, s_] := Times @@ (s^(IntegerExponent[n, #] & /@ s)) == n; Select[s1, ! aQ[#, s] &] (* _Amiram Eldar_, Aug 31 2019 *)
%Y A152023 Cf. A000695, A152021, A152022.
%K A152023 nonn
%O A152023 1,1
%A A152023 _Vladimir Shevelev_, Nov 20 2008, Jun 11 2009
%E A152023 a(12)-a(14) inserted and more terms added by _Amiram Eldar_, Aug 31 2019