A062685 Smallest square with digit sum n (or 0 if no such square exists).

1, 0, 0, 4, 0, 0, 16, 0, 9, 64, 0, 0, 49, 0, 0, 169, 0, 576, 289, 0, 0, 1849, 0, 0, 4489, 0, 3969, 17956, 0, 0, 6889, 0, 0, 27889, 0, 69696, 98596, 0, 0, 97969, 0, 0, 499849, 0, 1887876, 698896, 0, 0, 2778889, 0, 0, 4999696, 0, 9696996, 19998784, 0, 0

Offset: 1

Author

Erich Friedman, Jul 04 2001

Keywords

• base
• nonn

Comments

a(n) > 0 iff n mod 9 is 0, 1, 4, or 7. - Jon E. Schoenfield, Jul 06 2018

Examples

			16 is the smallest square with digit sum 7, so a(7)=16.
		

Links

• Jon E. Schoenfield, Table of n, a(n) for n = 1..228 (first 213 terms from Giovanni Resta)

Crossrefs

Cf. A004159, A056991.

Programs

Mathematica

Array[If[FreeQ[{1, 4, 7, 9}, FixedPoint[Total@ IntegerDigits@ # &, #]], 0, Block[{k = 1, s}, While[Total@ IntegerDigits@ Set[s, k^2] != #, k++]; s]] &, 57] (* Michael De Vlieger, Jul 06 2018 *)