This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A225190 #13 Jan 15 2025 19:42:12 %S A225190 0,0,0,20,64,1668,27712,355279,779264,170190707,6100448256, %T A225190 159424073982,2545667031040,239361355053790,812743283245056, %U A225190 58702956893404802,17949710147773530112,488189490082385976772,38768887410023899070464,313775221076492698014434,11531764219557396646723584 %N A225190 a(n) = (n+2)^(n+2) mod n^n. %C A225190 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 A225190 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 A225190 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 A225190 a(3) = 5^5 mod 3^3 = 3125 mod 27 = 20. %o A225190 (Python) %o A225190 for i in range(21): print(((i+2)**(i+2) % (i**i)), end=', ') %Y A225190 Cf. A066611, A176823, A176824. %K A225190 nonn,less %O A225190 0,4 %A A225190 _Alex Ratushnyak_, May 01 2013