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 A220780 #13 Jul 11 2022 11:27:12
%S A220780 2,1,4,2,2,1,6,3,2,1,4,2,2,1,8,4,2,1,4,2,2,1,6,3,2,1,4,2,2,1,10,5,2,1,
%T A220780 4,2,2,1,6,3,2,1,4,2,2,1,8,4,2,1,4,2,2,1,6,3,2,1,4,2,2,1,12,6,2,1,4,2,
%U A220780 2,1,6,3,2,1,4,2,2,1,8,4,2,1,4,2,2,1
%N A220780 Nonzero terms of A220779: exponent of highest power of 2 dividing an even sum 1^n + 2^n + ... + n^n.
%C A220780 2-adic valuation of Sum_{k=1..n} k^n for n == 0 or 3 mod 4.
%C A220780 See references, links, formulas, and example in A220779.
%t A220780 Table[n = 2*k + Mod[k, 2]; IntegerExponent[ Sum[a^n, {a, 1, n}], 2], {k, 150}]
%o A220780 (Python)
%o A220780 from sympy import harmonic
%o A220780 def A220780(n): return (~(m:=int(harmonic(k:=(n<<1)+(n&1),-k)))&m-1).bit_length() # _Chai Wah Wu_, Jul 11 2022
%Y A220780 Cf. A001511, A031971, A220779.
%K A220780 nonn
%O A220780 1,1
%A A220780 _Jonathan Sondow_, Dec 20 2012