Let b(n) be the number of permutations {c_1..c_n} of {1..n} for which c_1 - c_2 + ... + (-1)^(n-1)*c_n are triangular numbers (A000217). Then a(n) = b(n)/A010551(n).
A294811
Let b(n) be the number of permutations {c_1..c_n} of {1..n} for which c_1 - c_2 + ... + (-1)^(n-1)*c_n are triangular numbers (A000217). Then a(n) = b(n)/A010551(n).
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =6a(7) =11a(8) =16a(9) =30a(10) =48a(11) =97a(12) =157a(13) =322a(14) =524a(15) =1077a(16) =1777a(17) =3684a(18) =6157a(19) =12876a(20) =21684a(21) =45520a(22) =77212a(23) =162533a(24) =277608a(25) =585993a(26) =1006784a(27) =2129433a(28) =3677453a(29) =7788711
External references
- oeis: A294811