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First (leftmost) digit - second digit + third digit - fourth digit .... = 12.
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%I #8 May 19 2019 11:34:55

%S 309,408,419,507,518,529,606,617,628,639,705,716,727,738,749,804,815,

%T 826,837,848,859,903,914,925,936,947,958,969,3090,4080,4091,4190,5070,

%U 5081,5092,5180,5191,5290,6060,6071,6082,6093,6170,6181,6192,6280,6291

%N First (leftmost) digit - second digit + third digit - fourth digit .... = 12.

%t okQ[n_]:=Plus@@(Times@@#&/@Partition[Most[Riffle[IntegerDigits[10n],{1,-1}]],2])==12; Select[Range[7000],okQ] (* _Harvey P. Dale_, Jan 17 2011 *)

%t okQ[n_] := Module[{d = IntegerDigits[n]}, Plus @@ Take[d, {1, Length[d], 2}] - Plus @@ Take[d, {2, Length[d], 2}] == 12]; Select[Range[7000], okQ]

%Y Cf. A008593, A060978-A060980, A060982, A061470-A061479, A061870-A061882.

%K base,nonn,easy

%O 1,1

%A Larry Reeves (larryr(AT)acm.org), May 15 2001