A368787 a(n) = (n+1) * (n!)^2 * Sum_{k=1..n} 1/((k+1) * (k!)^2).
0, 1, 7, 85, 1701, 51031, 2143303, 120024969, 8641797769, 777761799211, 85553797913211, 11293101324543853, 1761723806628841069, 320633732806449074559, 67333083889354305657391, 16159940133445033357773841, 4395503716297049073314484753
Offset: 0
Keywords
Programs
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PARI
a(n) = (n+1)*n!^2*sum(k=1, n, 1/((k+1)*k!^2));
Formula
a(0) = 0; a(n) = (n+1) * n * a(n-1) + 1.
a(n) = A228229(n) - (n+1) * (n!)^2.