1906128

Appears in sequences

• Consider 2n tennis players; a(n) is the number of matches needed to let every possible pair play each other.at n=30A062346
• Let S(n)=sigma(|n|)-3*n; sequence gives numbers n such that S(S(S(S(n))))=n. May be called {3,1}-Sociable number of orders 1 or 2 or 4.at n=7A114528
• Triangular numbers of form n(n+2)(n+4).at n=6A165892
• The number of binary pattern classes in the (2,n)-rectangular grid with 5 '1's and (2n-5) '0's: two patterns are in same class if one of them can be obtained by a reflection or 180-degree rotation of the other.at n=29A222715
• Triangular numbers k such that phi(k) is a square number, where phi(k) is the Euler totient function (A000010).at n=33A287473