A053889 Squares composed of digits {1,2,9}.
1, 9, 121, 29929, 9991921, 1212919929, 1929229929, 1991212129, 2929299129, 1229129212921, 92222199291121, 219992999929921, 99221129991291219129, 2291192212129911919221121, 9992221299191112291912929211222129, 211192199129121999192121999211919121, 21112999921929291129929211912291229929191119991929921
Offset: 1
Links
- Patrick De Geest, Squares containing at most three distinct digits, Index entries for related sequences.
- Hisanori Mishima, Squares consisting of 3 different digits.
- Author?, Source(txt)
Crossrefs
Cf. A053888.
Programs
-
Mathematica
Flatten[Table[Select[FromDigits/@Tuples[{1,2,9},n], IntegerQ[Sqrt[#]]&],{n,12}]] (* This program generates only the first 9 terms of the sequence *) (* Harvey P. Dale, Oct 19 2011 *)
Formula
a(n) = A053888(n)^2. - Elmo R. Oliveira, Jul 18 2025
Extensions
a(13) from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 04 2005
a(14) from Jon E. Schoenfield, Sep 03 2006
a(15)-a(16) from Mishima's webpage added by Max Alekseyev, Jun 17 2011
a(17) from Zhao Hui Du, Feb 29 2024