**(-1)^(n+1)/2*sum(k=1,2n,C(2n+1,k)*B(k)*4^k) where C(n,k) are the binomial coefficients, B(k) the Bernoulli numbers.**

*1, 13, 213, 6233, 277865, 17567973, 1495207357, 164827853233, 22846356916689*

*2 seqfan posts*

Index of A-numbers in seqfan: by ascending order by month by frequency by keyword

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