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 A056828 #27 Feb 16 2025 08:32:43 %S A056828 7,15,23,87,111,119 %N A056828 Numbers that are not the sum of at most three powerful (1) numbers. %C A056828 Mollin and Walsh conjectured that there are no further terms. %C A056828 Heath-Brown proved that the sequence is finite. %C A056828 No other terms less than 40000000. - Paul.Jobling(AT)WhiteCross.com, May 14 2001 %D A056828 D. R. Heath-Brown, "Ternary Quadratic Forms and Sums of Three Square-Full Numbers." In Séminaire de Théorie des Nombres, Paris 1986-87 (Ed. C. Goldstein). Boston, MA: Birkhauser, pp. 137-163, 1988. %H A056828 R. A. Mollin and P. G. Walsh, <a href="http://dx.doi.org/10.1155/S0161171286000984">On Powerful Numbers</a>, Intern. J. Math. and Math. Sci, 9:801-806, 1986. %H A056828 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PowerfulNumber.html">Powerful Number.</a> %e A056828 Smallest powerful numbers are 1, 4, 8, 9, 16, 25,... so 7, 15 and 23 are not the sum of one, two or three of them. %Y A056828 Cf. A001694, A076871, A113505. %K A056828 fini,nonn %O A056828 1,1 %A A056828 _Henry Bottomley_, Aug 30 2000