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 A370250 #14 Mar 12 2024 15:38:13 %S A370250 0,1,5873656512,7253758561,29961747275 %N A370250 Numbers k such that the sum of the digits times the square of the sum of the fourth powers of the digits equals k. %C A370250 There are exactly 5 such numbers (Property 17 of Clerc). %H A370250 René-Louis Clerc, <a href="https://hal.science/hal-04235744">Quelques nombres de Niven-Harshad particuliers</a>, 2023. %e A370250 7253758561 = (7+2+5+3+7+5+8+5+6+1)*(7^4 + 2^4 + 5^4 + 3^4 + 7^4 + 5^4 + 8^4 + 5^4 + 6^4 + 1^4)^2 = 49*148035889 = 7253758561. %o A370250 (PARI) niven142(k) = my(d=digits(k)); vecsum(d)*sum(i=1, #d, d[i]^4)^2 == k; %o A370250 for(k=0,10^12,if(niven142(k)==1,print1(k, ", "))) %Y A370250 Cf. A368939, A115518, A257766, A061209, A061210, A254000, A130680, A366507, A366512. %K A370250 nonn,base,fini,full %O A370250 1,3 %A A370250 _René-Louis Clerc_, Feb 13 2024