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Search: id:A073908
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| A073908 |
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Smallest number m such that m and the product of digits of m are both divisible by 7n, or 0 if no such number exists. |
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+0
5
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| 7, 378, 273, 476, 175, 378, 3577, 728, 1197, 0, 0, 672, 0, 7742, 735, 784, 0, 3276, 0, 0, 7497, 0, 0, 7896, 1575, 0, 7938, 69776, 0, 0, 0, 12768, 0, 0, 37975, 3276, 0, 0, 0, 0, 0, 71736, 0, 0, 9765, 0, 0, 8736, 47677, 0, 0, 0, 0, 7938, 0, 74872, 0, 0, 0, 0, 0, 0, 7497
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Here 0 is regarded as not divisible by any number.
a[n]=0 if n is divisible by 10 or contains a prime divisor >9. - Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Aug 23 2002
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EXAMPLE
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a(8) = 728 is divisible by 7*8 =56 and also 7*2*8 = 112 = 2*56.
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MAPLE
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f := 7:for i from 1 to 400 do b := ifactors(f*i)[2]:if b[nops(b)][1]>9 or (f*i mod 10) =0 then a[i] := 0:else j := 0:while true do j := j+f*i:c := convert(j, base, 10): d := product(c[k], k=1..nops(c)):if (d mod f*i)=0 and d>0 then a[i] := j:break:fi: od:fi:od:seq(a[k], k=1..400);
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CROSSREFS
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Cf. A073906, A073907, A073909, A073910, A073911, A073912.
Sequence in context: A082443 A082624 A084001 this_sequence A027510 A140638 A112905
Adjacent sequences: A073905 A073906 A073907 this_sequence A073909 A073910 A073911
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 18 2002
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EXTENSIONS
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More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Aug 23 2002
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