%I A064509
%S A064509 2,3,5,7,10,13,15,17,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90,
%T A064509 95,100,105,110,115,120,125,130,135,140,145,150,155,160,165,170,175,
%U A064509 180,185,190,195,200,205,210,215,220,225,230,235,240,245,260,265
%N A064509 Marks (in fathoms) on lead line used by ships on Mississippi.
%C A064509 Certain depths have (or had) a visual and tactile indicator at positions 
               on the lead line. All depths with such attachments are "marks". All 
               others are "deeps." A leadsman measuring 12 feet of water calls "by 
               the mark two (or twain)." If the depth on the lead is 36 feet (6 
               fathoms) he would call "by the deep six!".
%C A064509 Samuel Clemens chose the nom de plume Mark Twain because, as a riverboat 
               skipper on the Mississippi, when the water was 12 feet deep, it was 
               safe sailing for those boats.
%D A064509 Bowditch, The American Practical Navigator, 1931 edition.
%D A064509 Postings to newsgroup rec.org.sca, circa Oct 22, 1994 by djheydt(AT)uclink.berkeley.edu 
               (Dorothy J. Heydt), Jeff Suzuki (jeffs(AT)math.bu.EDU) and Hal Ravn.
%H A064509 Mark S. Harris, <a href="http://www.florilegium.org/files/COMMERCE/measures-msg.text">
               Period measures and cautions for recipes</a>
%F A064509 For n >= 9, a(n) = 5(n-5).
%Y A064509 Sequence in context: A117959 A117952 A162999 this_sequence A096221 A120367 
               A072831
%Y A064509 Adjacent sequences: A064506 A064507 A064508 this_sequence A064510 A064511 
               A064512
%K A064509 nonn,nice
%O A064509 1,1
%A A064509 Peter Shor (shor(AT)math.mit.edu), Oct 06 2001