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A381073 Numbers k such that k and k+2 are both terms in A380846.

%I A381073 #6 Feb 17 2025 03:29:09
%S A381073 8596,9772,10444,17836,19626,21196,23716,27186,35754,36484,38164,
%T A381073 42700,45892,54796,56586,85708,91252,98586,100770,104970,112698,
%U A381073 132412,136612,139074,140980,141652,144676,149716,152850,165172,166122,171724,182032,182644,184770,190482
%N A381073 Numbers k such that k and k+2 are both terms in A380846.
%C A381073 Numbers k such that A380845(k) = 2*k and A380845(k+2) = 2*(k+2).
%H A381073 Amiram Eldar, <a href="/A381073/b381073.txt">Table of n, a(n) for n = 1..10000</a>
%t A381073 f[n_] := Module[{h = DigitCount[n, 2, 1]}, DivisorSum[n, # &, DigitCount[#, 2, 1] == h &] == 2*n]; seq[lim_] := Module[{q = Table[False, {4}], s = {}}, q[[1 ;; 2]] = f /@ Range[2]; Do[q[[3 ;; 4]] = f /@ Range[k, k + 1]; If[q[[1]] && q[[3]], AppendTo[s, k - 2]]; If[q[[2]] && q[[4]], AppendTo[s, k - 1]]; q[[1 ;; 2]] = q[[3 ;; 4]], {k, 3, lim, 2}]; s]; seq[50000]
%o A381073 (PARI) is1(k) = {my(h = hammingweight(k)); sumdiv(k, d, d*(hammingweight(d) == h)) == 2*k;}
%o A381073 list(lim) = {my(q1 = is1(1), q2 = is1(2), q3, q4); forstep(k = 3, lim, 2, q3 = is1(k); q4 = is1(k+1); if(q1 && q3, print1(k-2, ", ")); if(q2 && q4, print1(k-1, ", ")); q1 = q3; q2 = q4);}
%Y A381073 Subsequence of A380846.
%Y A381073 A381074 is a subsequence.
%Y A381073 Cf. A380845.
%K A381073 nonn,base
%O A381073 1,1
%A A381073 _Amiram Eldar_, Feb 13 2025