%I #13 Jan 15 2025 19:42:12
%S 0,0,0,20,64,1668,27712,355279,779264,170190707,6100448256,
%T 159424073982,2545667031040,239361355053790,812743283245056,
%U 58702956893404802,17949710147773530112,488189490082385976772,38768887410023899070464,313775221076492698014434,11531764219557396646723584
%N a(n) = (n+2)^(n+2) mod n^n.
%C The sequence of indices of odd terms b(n) begins: 7, 9, 25, 27, 39, 43, 45, 49, 53, 57, 59, 65, 67, 71, ...
%C a(n) may be odd only if n is odd. For even n's, both (n+2)^(n+2) and n^n are even, therefore a(n) is even.
%C c(n) = (b(n)-1)/2 begins: 3, 4, 12, 13, 19, 21, 22, 24, 26, 28, 29, 32, 33, 35, 36, 37, 38, 41, ...
%e a(3) = 5^5 mod 3^3 = 3125 mod 27 = 20.
%o (Python)
%o for i in range(21): print(((i+2)**(i+2) % (i**i)), end=', ')
%Y Cf. A066611, A176823, A176824.
%K nonn,less
%O 0,4
%A _Alex Ratushnyak_, May 01 2013