Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #11 Dec 23 2024 14:53:41
%S 0,1,11,111,2,12,112,1112,22,3,13,113,222,23,123,1123,4,14,33,133,24,
%T 124,233,1233,224,5,15,115,1115,25,125,1125,44,144,35,135,6,16,116,
%U 1116,26,45,145,335,226,36,136,1136,444,7,17,117,46,27,127,1127,246
%N Smallest number whose sum of squares of digits is n.
%H Zak Seidov, <a href="/A055016/b055016.txt">Table of n, a(n) for n = 0..600</a>
%H E. Angelini, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2015-June/014998.html">Sum of squares -- and a concatenation</a>, SeqFan list, June 23, 2015.
%o (PARI) A055016(n,q=9,m)={ n>1||return(n); forstep(q=min(sqrtint(n),q),1,-1, m && n \ q^2 * #Str(q) > #Str(m) && break; t=eval(Str(A055016(n-q^2,q),q)); (!m || t<m) && m=t); m } \\ _M. F. Hasler_, Jun 24 2015
%Y Cf. A003132 is inverse in sense that n=A003132(a(n)), though not necessarily a(A003132(n)).
%K base,nonn,changed
%O 0,3
%A _Henry Bottomley_, May 31 2000