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 A005077 #21 Jun 21 2022 05:10:40 %S A005077 0,16,0,16,625,16,0,16,0,641,14641,16,0,16,625,16,83521,16,0,641,0, %T A005077 14657,279841,16,625,16,0,16,707281,641,0,16,14641,83537,625,16,0,16, %U A005077 0,641,2825761,16,0,14657,625,279857,4879681,16,0,641,83521,16,7890481,16,15266,16,0,707297,12117361,641,0,16,0,16,625,14657,0,83537 %N A005077 Sum of 4th powers of primes = 2 mod 3 dividing n. %H A005077 Antti Karttunen, <a href="/A005077/b005077.txt">Table of n, a(n) for n = 1..10000</a> %F A005077 Additive with a(p^e) = p^4 if p = 2 (mod 3), 0 otherwise. %F A005077 a(n) = A005065(n) - A005073(n) - 81*A079978(n). - _Antti Karttunen_, Jul 10 2017 %t A005077 Array[DivisorSum[#, #^4 &, And[PrimeQ@ #, Mod[#, 3] == 2] &] &, 68] (* _Michael De Vlieger_, Jul 11 2017 *) %t A005077 f[p_, e_] := If[Mod[p, 3] == 2, p^4, 0]; a[n_] := Plus @@ f @@@ FactorInteger[n]; a[1] = 0; Array[a, 100] (* _Amiram Eldar_, Jun 21 2022 *) %o A005077 (Scheme) (define (A005077 n) (if (= 1 n) 0 (+ (A000583 (if (= 2 (modulo (A020639 n) 3)) (A020639 n) 0)) (A005077 (A028234 n))))) ;; _Antti Karttunen_, Jul 10 2017 %o A005077 (PARI) a(n) = my(f=factor(n)); sum(k=1, #f~, if (((p=f[k,1])%3) == 2, p^4)); \\ _Michel Marcus_, Jul 11 2017 %Y A005077 Cf. A000583, A005065, A005073, A005074, A005075, A005076, A008472, A079978. %K A005077 nonn %O A005077 1,2 %A A005077 _N. J. A. Sloane_ %E A005077 More terms from _Antti Karttunen_, Jul 10 2017