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 A063274 #14 May 13 2013 01:54:05 %S A063274 1,2,3,1,2,3,4,1,1,2,3,2,2,3,4,1,2,2,3,2,3,3,4,2,1,2,1,2,2,3,2,1,2,2, %T A063274 2,1,2,3,3,2,2,3,2,2,2,3,3,2,1,2,3,2,2,2,3,3,2,2,2,3,2,3,2,1,2,3,3,2, %U A063274 3,3,3,1,2,2,3,2,3,3,3,2,1,2,3,3,2,3,4,2,2,2,2,3,3,3,3,2,2,2,2,1,2,3,3,2,3 %N A063274 Number of powerful numbers (definition 1) required to sum to n. %C A063274 Heath-Brown proves that a(n) <= 3 for all large n. It seems that n > 119 suffices. - _Charles R Greathouse IV_, Nov 19 2012 %D A063274 D. R. Heath-Brown, Ternary quadratic forms and sums of three square-full numbers, Séminaire de Théorie des Nombres, Paris 1986-87, pp. 137-163; Progr. Math., 75, Birkhäuser Boston, Boston, MA, 1988. %H A063274 Charles R Greathouse IV, <a href="/A063274/b063274.txt">Table of n, a(n) for n = 1..10000</a> %e A063274 The powerful numbers (A001694) start 1,4,8,9,... 11=1+1+9 and is not the sum of fewer terms, so a(11)=3. %o A063274 (PARI) W=vector(99); W[1]=1; for(n=2,#W, if(ispowerful(n), W[n]=1; next); b=n; for(i=1,n\2, b=min(b,W[i]+W[n-i])); W[n]=b); W \\ _Charles R Greathouse IV_, Nov 19 2012 %Y A063274 Cf. A001694, A056828, A063275. %K A063274 nonn %O A063274 1,2 %A A063274 _Jud McCranie_, Jul 13 2001