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A305739 a(n) = n!*T(n) - 1, where T(n) is the n-th triangular number. 0

%I

%S 0,5,35,239,1799,15119,141119,1451519,16329599,199583999,2634508799,

%T 37362124799,566658892799,9153720575999,156920924159999,

%U 2845499424767999,54420176498687999,1094805903679487999,23112569077678079999,510909421717094399999

%N a(n) = n!*T(n) - 1, where T(n) is the n-th triangular number.

%F a(n) = n*(n+1)!/2 - 1. - _Michel Marcus_, Jun 23 2018

%F a(n) = A180119(n)-1 = A001286(n+1)-1. - _Alois P. Heinz_, Jun 24 2018

%p seq(n*(n+1)!/2-1,n=1..21);

%o (PARI) a(n) = n*(n+1)!/2 - 1; \\ _Michel Marcus_, Jun 23 2018

%Y Cf. A000142, A000217, A001286, A180119.

%Y See A305738 for the indices of primes in this sequence.

%K nonn

%O 1,2

%A _Maheswara Rao Valluri_, Jun 22 2018

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Last modified February 26 01:41 EST 2020. Contains 332270 sequences. (Running on oeis4.)