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a(0) = 1, for n >= 1: a(n) = differences between consecutive primes (A001223(n)) = A158611(n+2) - A158611(n+1). Partial sums of a(n-1) = A006093(n) for n >= 1. [From Jaroslav Krizek, Aug 04 2009]
First differences of noncomposite numbers. [Juri-Stepan Gerasimov, Feb 17 2010]