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Engineering Mathematics · Combinatorics
Official IIT answer key · IIT Delhi · Audited Aug 2026
GATE CSE 2020 Q42 · NAT · 2 marks
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Topic notes
GATE evaluates Generating Functions by testing the candidate's ability to find closed-form representations of ordinary generating functions (OGFs) for piecewise or parity-dependent sequences. Questions require decomposing sequences linearly and applying operations like substitution (e.g., x2) and differentiation to handle polynomial coefficients. These items test analytical fluency with infinite series and discrete mathematics manipulations.
Full Combinatorics guide →The number of permutations of the characters in LILAC so that no character appears in its original position, if the two L’s are indistinguishable, is …
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