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A064704
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Numbers beginning and ending with their multiplicative digital root.
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1
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1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 88, 111, 232, 535, 575, 646, 686, 818, 838, 1111, 2132, 2312, 2472, 2692, 2742, 2962, 5135, 5175, 5315, 5715, 5795, 5975, 6146, 6186, 6226, 6246, 6416, 6426, 6696, 6776, 6816, 6966, 8118, 8138, 8278, 8318, 8728, 11111
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| If NA(1)A(2)...A(j)N is MDR strong then also Na(1)a(2)...a(j)N is MDR strong where a(1)a(2)...a(j) is any permutation of A(1)A(2)...A(j) and if any of A(1),A(2),...,A(j) say A(1) is composite then also NB(1)...B(k)A(2)...A(j) is MDR strong where A(1)=B(1)*B(2)*...*B(k), so MDR strong numbers with greater number of digits are likely to be more frequent.
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 1..1000
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MATHEMATICA
| dr[n_]:=NestWhile[Times@@IntegerDigits[#]&, n, #>9&]; bemdrQ[n_]:=Module[ {idn=IntegerDigits[n]}, First[idn]==Last[idn]==dr[n]]; Select[Range[ 12000], bemdrQ] (* From Harvey P. Dale, Oct 21 2011 *)
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CROSSREFS
| Cf. A031347.
Sequence in context: A103357 A055931 A167152 * A083136 A117057 A029967
Adjacent sequences: A064701 A064702 A064703 * A064705 A064706 A064707
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KEYWORD
| nonn,base
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AUTHOR
| Santi Spadaro (spados(AT)katamail.com), Oct 13 2001
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