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

1,4

Comments

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

Links

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

Example

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

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 *)

Crossrefs

Cf. A004159, A056991.

Sequence in context: A336731 A069026 A133851 * A192016 A028699 A019259

Adjacent sequences: A062682 A062683 A062684 * A062686 A062687 A062688

Keyword

base,nonn

Author

Erich Friedman, Jul 04 2001

Status

approved