A164839 Left-truncatable squares: every suffix is square.

1, 4, 9, 49, 64, 81

Offset

1,2

Comments

This sequence is finite and 81 is the last term. If another term were to exist it must contain 3 digits and contract to 49, 64, or 81. No such 3 digit square exists. [Sean A. Irvine, Sep 08 2009]

Links

Table of n, a(n) for n=1..6.

Example

a(5) = 64 since 64 is a perfect square and 4 is also a perfect square.

Mathematica

Select[Range[1000], Sum[Boole[IntegerQ[Sqrt[t=FromDigits[Drop[IntegerDigits[#], i]]]] && t != 0], {i, 0, IntegerLength[#]-1}] == IntegerLength[#] &] (* Stefano Spezia, Jun 27 2025 *)

Crossrefs

Cf. A000290, A164840.

Sequence in context: A256880 A327699 A013495 * A225885 A247267 A115687

Adjacent sequences: A164836 A164837 A164838 * A164840 A164841 A164842

Keyword

nonn,base,fini,full

Author

Gaurav Kumar, Aug 28 2009

Status

approved