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%I #27 May 10 2019 06:50:26
%S 100,93,86,79,72,65,58,51,44,37,30,23,16,9,2
%N Count backwards from 100 in steps of 7.
%C Sometimes used to gauge the concentration ability of a patient with Alzheimer's disease. The combination of a simple arithmetic operation with an unusual decrement forces the patient to rely on short-term memory for the computation. Most patients would stop when they get to 2, but the psychiatrist might be satisfied with the first five or so terms. In this capacity the sequence is mentioned a few times in the movie "Safe House" (1998) in which Mace Sowell (Patrick Stewart) tries to memorize the sequence and is asked it by the psychiatrist (Hector Elizondo). In real life, other decrements can be used; Fish (1996) suggests 3 and 4.
%C In the next-to-last episode of "Boston Legal," Denny Crane (William Shatner) is asked this sequence by a doctor while in an MRI machine. He gets confused at 86, following it with 81. (Both Shatner and Stewart have played captain of the Enterprise on TV.) - Wilfredo Lopez (chakotay147138274(AT)yahoo.com), Dec 03 2008
%D Sharon Fish, "Alzheimer's: Caring for Your Loved One, Caring for Yourself", Wheaton, Illinois: Harold Shaw Publishers, 1996, p. 34
%H Max Hayman, <a href="https://doi.org/10.1001/archneurpsyc.1942.02290030112010">Two minute clinical test for measurement of intellectual impairment in psychiatric disorders</a>, Arch. Neurpsych. 47:3 (1942), pp. 454-464.
%H Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/NonRecursions.html">Non Recursions</a>
%H Robert Thomas Manning, <a href="https://doi.org/10.1001/archinte.1982.00340190148022">The serial sevens test</a>, Arch Intern Med. 142:6 (1982), p. 1192.
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Serial_sevens">Serial sevens</a>
%F a(n) = 100 - 7n.
%t Range[100, 2, -7] (* _Harvey P. Dale_, Apr 11 2014 *)
%o (PARI) a(n)=100-7*n \\ _Charles R Greathouse IV_, Feb 25 2019
%o (Scala) (0 to 14).map(100 - 7 * _) // _Alonso del Arte_, May 09 2019
%Y First fifteen terms of A017005 backwards.
%K easy,fini,full,nonn
%O 0,1
%A Robert Happelberg (roberthappelberg(AT)yahoo.com), Feb 23 2006
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