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 A050467 #18 Nov 06 2023 03:21:59 %S A050467 0,0,1,0,0,16,1,0,81,0,1,256,0,16,626,0,0,1296,1,0,2482,16,1,4096,0,0, %T A050467 6562,256,0,10016,1,0,14722,0,626,20736,0,16,28562,0,0,39712,1,256, %U A050467 50706,16,1,65536,2401,0,83522,0,0,104992,626,4096,130402 %N A050467 a(n) = Sum_{d|n, n/d=3 mod 4} d^4. %H A050467 Amiram Eldar, <a href="/A050467/b050467.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale) %F A050467 From _Amiram Eldar_, Nov 05 2023: (Start) %F A050467 a(n) = A285989(n) - A050463(n). %F A050467 a(n) = A050463(n) - A050468(n). %F A050467 a(n) = (A285989(n) - A050468(n))/2. %F A050467 Sum_{k=1..n} a(k) ~ c * n^5 / 5, where c = 31*zeta(5)/64 - 5*Pi^5/3072 = 0.00418296735902... . (End) %t A050467 Table[Total[Select[Divisors[n],Mod[n/#,4]==3&]^4],{n,60}] (* _Harvey P. Dale_, Jun 10 2023 *) %t A050467 a[n_] := DivisorSum[n, #^4 &, Mod[n/#, 4] == 3 &]; Array[a, 50] (* _Amiram Eldar_, Nov 05 2023 *) %o A050467 (PARI) a(n) = sumdiv(n, d, (n/d % 4 == 3) * d^4); \\ _Amiram Eldar_, Nov 05 2023 %Y A050467 Cf. A013663, A050463, A050468, A285989. %Y A050467 Cf. A050464, A050465, A050466. %K A050467 nonn,easy %O A050467 1,6 %A A050467 _N. J. A. Sloane_, Dec 23 1999 %E A050467 Offset corrected by _Amiram Eldar_, Nov 05 2023