Number of permutations p of [n] satisfying Sum_{i=1..n} (p(i)-i)^2 = 2*n.

Terms

a(0) =1a(1) =0a(2) =0a(3) =2a(4) =2a(5) =6a(6) =14a(7) =46a(8) =129a(9) =284a(10) =819a(11) =2238a(12) =5696a(13) =15418a(14) =41329a(15) =110038a(16) =294940a(17) =790886a(18) =2129552a(19) =5725742a(20) =15410887a(21) =41608106a(22) =112287133a(23) =303218774a(24) =819977652a(25) =2218544958a(26) =6005987603a(27) =16270113462a(28) =44102776214a(29) =119613683906