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%I #8 Jan 01 2024 13:44:47
%S 1,2,9,18,891,17982,89099109,1798199982018,890991089999910900891,
%T 1798199982017999999998201800017982,
%U 8909910899999109008909999999999999109008910000089099109
%N a(1)=1, a(2)=2, then use "merge and minus": a(n)=merge(a(n-2),a(n-1))-a(n-2)-a(n-1).
%C A rapidly growing sequence. An even more rapidly growing sequence with "merge and minus" rule is A075538.
%e a(3)=9 because a(1)=1, a(2)=2 and a(3)=merge(a(1), a(2))-a(1)-a(2)=12-1-2=9; a(4)=18 because a(2)=2, a(3)=9 and a(4)=merge(a(2), a(3))-a(2)-a(3)=29-2-9=18.
%t se={1, 2}; a=1; b=2; Do[ab=ToExpression[ToString[a]<>ToString[b]]-a-b; se=Append[se, ab]; a=b; b=ab, {i, 10}]; se
%Y Cf. A075538.
%K nonn
%O 1,2
%A _Zak Seidov_, Sep 20 2002