A151997 a(n) = (n 1's followed by a 3)^2.

9, 169, 12769, 1238769, 123498769, 12346098769, 1234572098769, 123456832098769, 12345679432098769, 1234567905432098769, 123456790165432098769

Offset: 0

Author

Zak Seidov, Sep 09 2009

Keywords

• nonn
• base

Comments

Is it true that the decimal expansion of a(n) contains no palindromic substrings of length greater than one?

Examples

			{3.9}
{13,169}
{113,12769}
{1113,1238769}
{11113,123498769}
{111113,12346098769}
{1111113,1234572098769}
{11111113,123456832098769}
{111111113,12345679432098769}
{1111111113,1234567905432098769}
{11111111113,123456790165432098769}
		

Crossrefs

Cf. A052061, A052062.

Programs

Mathematica

Table[FromDigits[PadLeft[{3},n,1]]^2,{n,20}] (* Harvey P. Dale, Sep 04 2022 *)

Formula

a(n) = (100^(n+1)+340*10^n+289)/81. a(n)= 111*a(n-1) -1110*a(n-2) +1000*a(n-3). G.f.: (9-830*x+4000*x^2)/((1-x) * (100*x-1) * (10*x-1)). [From R. J. Mathar, Sep 15 2009]