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 A331464 Numbers k such that k and k + 1 are both binary Smith numbers (A278909). 3

%I

%S 1369,1370,1390,1630,1929,2525,2526,2930,3013,3309,3501,3502,3686,

%T 3805,3953,3954,4043,4726,4854,5620,5621,5917,6068,6682,6774,6838,

%U 7025,7089,7115,7671,7738,7786,8075,9654,9915,10366,10982,11166,11227,11506,11673,11740,11763

%N Numbers k such that k and k + 1 are both binary Smith numbers (A278909).

%H Amiram Eldar, <a href="/A331464/b331464.txt">Table of n, a(n) for n = 1..10000</a>

%e 1369 is in the sequence since both 1369 and 1369 + 1 = 1370 are binary Smith numbers.

%t binWt[n_] := Total @ IntegerDigits[n, 2]; binSmithQ[n_] := CompositeQ[n] && Plus @@ (Last@# * binWt[ First@# ] & /@ FactorInteger[n]) == binWt[n]; seq = {}; isSmith1 = binSmithQ[1]; Do[isSmith2 = binSmithQ[n]; If[isSmith1 && isSmith2, AppendTo[seq, n-1]]; isSmith1 = isSmith2, {n, 2, 12000}]; seq

%Y Cf. A006753, A050219, A050220, A278909, A331463, A331465.

%K nonn,base

%O 1,1

%A _Amiram Eldar_, Jan 17 2020

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Last modified July 29 01:03 EDT 2021. Contains 346340 sequences. (Running on oeis4.)