A068898 - OEIS

A068898

Triangular numbers containing 2k digits in which the sum of the first k 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

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OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

2415 is a term 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

Intersection of A000217 and A240927.

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

Offset changed by Andrew Howroyd, Sep 21 2024

STATUS

approved