A068898 Triangular numbers containing 2n digits in which the sum of the first n digits = that of the rest.

55, 66, 2415, 3003, 5050, 5151, 5995, 8778, 9045, 113050, 138075, 171405, 174345, 177906, 183921, 198765, 203203, 216153, 219453, 234270, 237705, 239086, 252405, 255255, 266815, 267546, 275653, 279378, 284635, 293761, 294528, 306153, 309291, 329266, 348195

Offset

0,1

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Example

2415 is a member with 2+4 = 1+5

Mathematica

dsQ[n_]:=Module[{idn=IntegerDigits[n], len=IntegerLength[n]/2}, Total[Take[ idn, len]] ==Total[ Take[idn, -len]]]; Select[Flatten[ Table[Table[(n(n+1))/2, {n, Ceiling[(Sqrt[8 10^i+1]-1)/2], Floor[ (Sqrt[8 10^(i+1)+1]-1)/2]}], {i, 1, 5, 2}]], dsQ] (* Harvey P. Dale, Sep 29 2011 *)

Crossrefs

Cf. A068896, A068897.

Sequence in context: A004434 A168109 A116055 * A068899 A053719 A217236

Adjacent sequences: A068895 A068896 A068897 * A068899 A068900 A068901

Keyword

easy,nonn,base

Author

Amarnath Murthy, Mar 21 2002

Extensions

Corrected and extended by Harvey P. Dale, Sep 29 2011

Status

approved