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A095256
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Number of numbers not divisible by 10 which stay multiples of themselves when freed of their last n digits.
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3
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23, 473, 7053, 93643, 1166714, 13969985, 162725300, 1857511487, 20877697534, 231802823099, 2548286736153, 27785452448917, 300880375389561, 3239062263180829, 34693207724723990, 369957928177109127
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| S. Das Dividing by Dropping Digits
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FORMULA
| a(n)=sum_(r=1, 10^n - 1) tau(r)=A006218(A002283(n)).
a(n) = A057494(n) - (n+1)^2 [From Max Alekseyev (maxale(AT)gmail.com), Jan 25 2010]
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EXAMPLE
| We have the following a(1)=23 two-digit numbers not ending in zero: 11, 12, 13, 14, 15, 16, 17, 18, 19, 22, 24, 26, 28, 33, 36, 39, 44, 48, 55, 66, 77, 88, 99 which are divisible by their tenth digit.
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MATHEMATICA
| k = s = 0; Do[ While[ k < 10^n - 1, k++; s = s + DivisorSigma[ 0, k ]]; Print[s], {n, 9}] (from Robert G. Wilson v Jun 05 2004)
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CROSSREFS
| Cf. A057494.
Sequence in context: A053067 A036906 A134733 * A015678 A014905 A200734
Adjacent sequences: A095253 A095254 A095255 * A095257 A095258 A095259
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KEYWORD
| base,nonn
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AUTHOR
| Lekraj Beedassy (blekraj(AT)yahoo.com), Jul 02 2004
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EXTENSIONS
| a(5)-a(9) from Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 05 2004
a(10) onward from Max Alekseyev (maxale(AT)gmail.com), Jan 25 2010
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