A080161 Indices of Wonderful Demlo numbers A002477 whose digit sums are squares.

1, 2, 3, 4, 5, 6, 7, 8, 9, 36, 51, 66, 81, 102, 123, 144, 225, 258, 291, 324, 363, 402, 441, 576, 593, 610, 627, 644, 661, 678, 695, 712, 729, 748, 767, 786, 805, 824, 843, 862, 881, 900, 1089, 1158, 1227, 1296, 1371, 1446, 1521, 1764, 1851, 1938, 2025

Offset: 1

Author

Eric W. Weisstein, Jan 31 2003

Keywords

• nonn
• base

Comments

The numbers 9*n^2 (A016766), with n > 0, are in this sequence. - Enrique Pérez Herrero, Sep 26 2020

Links

• Jeppe Stig Nielsen, Table of n, a(n) for n = 1..10000
• Eric Weisstein's World of Mathematics, Demlo Number

Crossrefs

Cf. A080160, A080162, A002477, A080151, A108690.

Programs

Mathematica

A080151[n_] := (9^2)*(n/9 - FractionalPart[n/9] + FractionalPart[n/9]^2)
Select[Range[10000], IntegerQ[Sqrt[A080151[#]]] &]
(* Enrique Pérez Herrero, Sep 26 2020 *)

PARI

for(k=1,10^5,issquare((k\9)*81+(k%9)^2)&&print1(k,", ")) \\ Jeppe Stig Nielsen, May 27 2023