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 A143026 #19 Nov 07 2023 11:17:52 %S A143026 1,625,6561,4100625 %N A143026 Positive integers k such that the fourth power of the number of positive divisors of k equals k. %C A143026 625=5^4, 6561=3^8, 4100625=(3^8)(5^4). %C A143026 There are no more terms in the sequence. %D A143026 T. Andreescu, D. Andrica and Z. Feng, 104 Number Theory Problems (from the training of the USA IMO team), Birkhäuser, Boston, 2007, Advanced problem # 19, pp. 85, 145, 146. %D A143026 Roozbeh Hazrat, Mathematica: A Problem-Centered Approach, Springer 2010, p. 39. %e A143026 625 has 5 divisors (1, 5, 25, 125 and 625) and 5^4 = 625. %t A143026 Select[Range[4200000],DivisorSigma[0,#]^4==#&] (* _Harvey P. Dale_, Oct 17 2011 *) %Y A143026 Cf. A066693, A180936. %K A143026 fini,nonn,full %O A143026 1,2 %A A143026 _Emeric Deutsch_, Aug 11 2008 %E A143026 Second reference added by _Harvey P. Dale_, Oct 17 2011