A242964 Consider a number n with m decimal digits. The sequence lists the numbers n having the suffix of length m-1 in the middle of the decimal expansion of n^2.

10, 20, 28, 30, 100, 200, 300, 302, 304, 306, 308, 511, 839, 864, 1000, 1100, 1500, 1600, 2000, 2100, 2438, 2500, 2600, 3000, 3002, 3004, 3006, 3008, 3100, 5099, 7046, 8020, 8073, 9082, 10000, 20000, 30000, 30002, 30004, 30006, 30008, 30604, 35000, 36000

Offset

1,1

Links

Table of n, a(n) for n=1..44.

Example

511 is in the sequence because 511^2 = 261121
and the suffix 11 is in the middle of the decimal expansion of 261121.

Mathematica

lst={}; Do[a=IntegerDigits[n^2]; b=Length[a]; l=IntegerLength[n]-1; c=IntegerLength[Mod[n, 10^l]]; If[Mod[n, 10^l]==0, c=1]; If[EvenQ[b-c]&&FromDigits[Take[a, {(b-c)/2+1, (b+c)/2}]]==Mod[n, 10^l], AppendTo[lst, n]], {n, 10, 10^6}]; lst

Crossrefs

Cf. A000290, A242942.

Sequence in context: A019491 A249989 A175229 * A063117 A157938 A095208

Adjacent sequences: A242961 A242962 A242963 * A242965 A242966 A242967

Keyword

nonn,base

Author

Michel Lagneau, May 28 2014

Status

approved