Number of bangbangs (!!) in shell substitution when starting with : '!!' and : "!!" '!!'.

A228162

Number of bangbangs (!!) in shell substitution when starting with : '!!' and : "!!" '!!'.

Terms

    a(0) =1a(1) =2a(2) =2a(3) =3a(4) =5a(5) =17a(6) =161a(7) =15681a(8) =159591041

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