A055016 Smallest number whose sum of squares of digits is n.

0, 1, 11, 111, 2, 12, 112, 1112, 22, 3, 13, 113, 222, 23, 123, 1123, 4, 14, 33, 133, 24, 124, 233, 1233, 224, 5, 15, 115, 1115, 25, 125, 1125, 44, 144, 35, 135, 6, 16, 116, 1116, 26, 45, 145, 335, 226, 36, 136, 1136, 444, 7, 17, 117, 46, 27, 127, 1127, 246

Offset: 0

Author

Henry Bottomley, May 31 2000

Keywords

• base
• nonn

Links

• Zak Seidov, Table of n, a(n) for n = 0..600
• E. Angelini, Sum of squares -- and a concatenation, SeqFan list, June 23, 2015.

Crossrefs

Cf. A003132 is inverse in sense that n=A003132(a(n)), though not necessarily a(A003132(n)).

Programs

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 || tM. F. Hasler, Jun 24 2015