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Search: id:A116440
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| A116440 |
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Numbers n which when sandwiched between two 5's give a multiple of n. |
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+0
1
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| 1, 5, 11, 13, 35, 55, 65, 77, 91, 137, 365, 685, 9091, 49505, 909091, 5882353, 10989011, 12987013, 20242915, 23923445, 34965035, 37593985, 52631579, 54945055, 64935065, 76923077, 90909091, 495049505, 1976284585, 4132231405
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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137 belongs since 51375 is a multiple 137 (137*375).
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MAPLE
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a:=proc(n) local nn: nn:=convert(n, base, 10): if type((5+10*n+5*10^(nops(nn)+1))/n, integer)=true then n else fi end: seq(a(n), n=1..10000); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 28 2006
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MATHEMATICA
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f[k_, d_] := Flatten@Table[Select[Divisors[k*(10^(i + 1) + 1)], IntegerLength[ # ] == i &], {i, d}]; f[5, 10] (*Chandler*)
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CROSSREFS
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Cf. A116436-A116444.
Adjacent sequences: A116437 A116438 A116439 this_sequence A116441 A116442 A116443
Sequence in context: A051654 A098973 A125742 this_sequence A098720 A115091 A034924
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KEYWORD
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base,nonn
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AUTHOR
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Giovanni Resta (g.resta(AT)iit.cnr.it), Feb 15 2006
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