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303. APL (Dyalog), 203 bytes, A000135
{n←1+⍵⋄++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++≢⊃{{(n≥⍵)/⍵},⍵,⍺+0,⍵}/(2÷3)*⍨1+⍳⌊1.5*⍨n}
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using ⎕IO←0. After removing fillers ...