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A020331 Numbers n such that base 3 representation is the juxtaposition of two identical strings. 0
4, 8, 30, 40, 50, 60, 70, 80, 252, 280, 308, 336, 364, 392, 420, 448, 476, 504, 532, 560, 588, 616, 644, 672, 700, 728, 2214, 2296, 2378, 2460, 2542, 2624, 2706, 2788, 2870, 2952, 3034, 3116, 3198, 3280, 3362, 3444, 3526, 3608, 3690, 3772, 3854, 3936, 4018 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..49.

MATHEMATICA

b3iQ[n_]:=Module[{idn3=IntegerDigits[n, 3], len}, len=Length[idn3]; EvenQ[ len] && Take[idn3, len/2]==Take[idn3, -len/2 ]]; Select[Range[5000], b3iQ] (* Harvey P. Dale, Feb 08 2015 *)

CROSSREFS

Sequence in context: A280085 A256456 A270522 * A248476 A082595 A262154

Adjacent sequences:  A020328 A020329 A020330 * A020332 A020333 A020334

KEYWORD

nonn,base

AUTHOR

David W. Wilson, Melia Aldridge, ma38(AT)spruce.evansville.edu

STATUS

approved

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Last modified March 27 16:36 EDT 2017. Contains 284177 sequences.