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Indices of terms in A093019 with value 7.
1

%I #16 Aug 17 2021 06:25:34

%S 6,11,25,30,49,54,68,73,87,92,105,110,129,134,148,153,167,172,186,191,

%T 209,214,228,233,247,252,266,271,285,290,308,313,327,332,346,351,365,

%U 370,389,394,407,412,426,431,445,450,469,474,488,493,501,515,520,539

%N Indices of terms in A093019 with value 7.

%C Integers which require a following 7 to have a valid Luhn mod 10 check digit.

%H Reinhard Zumkeller, <a href="/A093027/b093027.txt">Table of n, a(n) for n = 1..10000</a>

%H John Kilgo, <a href="https://web.archive.org/web/20040627030859/http://www.dotnetjohn.com/articles/articleid97.aspx">Using the Luhn Algorithm</a>, DotNetJohn.com.

%H Webopedia, <a href="http://www.webopedia.com/TERM/L/Luhn_formula.html">Luhn formula</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Luhn_algorithm">Luhn algorithm</a>

%H <a href="/index/De#decimal_expansion">Index entries for sequences related to decimal expansion of n</a>

%F A093019(a(n)) = 7. - _Reinhard Zumkeller_, Nov 08 2014

%e 11 is in the sequence because A093019(11)=7; 117 has a valid Luhn mod 10 check digit.

%o (Haskell)

%o a093027 n = a093027_list !! (n-1)

%o a093027_list = filter ((== 7) . a093019) [0..]

%o -- _Reinhard Zumkeller_, Nov 08 2014

%Y Cf. A093017-A093029.

%K easy,nonn,base

%O 1,1

%A _Ray Chandler_, Apr 03 2004

%E Offset changed by _Reinhard Zumkeller_, Nov 08 2014