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 A020333 Numbers n such that base 5 representation is the juxtaposition of two identical strings. 7
 6, 12, 18, 24, 130, 156, 182, 208, 234, 260, 286, 312, 338, 364, 390, 416, 442, 468, 494, 520, 546, 572, 598, 624, 3150, 3276, 3402, 3528, 3654, 3780, 3906, 4032, 4158, 4284, 4410, 4536, 4662, 4788, 4914, 5040, 5166, 5292, 5418, 5544, 5670, 5796, 5922, 6048 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 FORMULA a(n) = n*5^floor(log_5(n)+1) + n. - Ilya Gutkovskiy, Jan 26 2018 MATHEMATICA tis5Q[n_]:=Module[{idn=IntegerDigits[n, 5], len}, len=Length[idn]; EvenQ[len] && Take[idn, len/2]==Take[idn, -len/2]]; Select[Range[6500], tis5Q]  (* or *) Flatten[Table[FromDigits[#, 5]&/@Select[(Flatten[{#, #}]&/@Tuples[ Range[ 0, 4], n]), #[[1]]!=0&], {n, 3}]] (* The second program is significantly faster than the first. *) (* Harvey P. Dale, Apr 08 2013 *) CROSSREFS Cf. A020330, A020331, A020332, A020334, A020335, A020336, A020337, A020338. Sequence in context: A073455 A279894 A209309 * A044831 A033003 A108592 Adjacent sequences:  A020330 A020331 A020332 * A020334 A020335 A020336 KEYWORD nonn,base AUTHOR David W. Wilson, Melia Aldridge, ma38(AT)spruce.evansville.edu STATUS approved

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Last modified October 20 02:10 EDT 2019. Contains 328244 sequences. (Running on oeis4.)