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%I #16 Dec 15 2017 17:35:00
%S 2,2,2,2,4,6,8,14,18,20,38,52,60,112,150,170,320,432,492,924,1244,
%T 1414,2658,3582,4074,7656,10314,11728,22042,29698,33772,63470,85512,
%U 97240,182752,246222,279994,526216,708968,806208,1515176,2041392,2321386
%N 4-wave sequence beginning with 2s.
%C Primes are the numbers >=2 which have no nontrivial divisor: a(p)=0.
%C Also: a(n)= A032741(n)-1, n>=2 (from number of divisors <n, called proper divisors).
%H F. v. Lamoen, <a href="http://home.wxs.nl/~lamoen/wiskunde/wave.htm">Wave sequences</a>
%H <a href="/index/Rec#order_11">Index entries for linear recurrences with constant coefficients</a>, signature (1, -1, 3, -3, 3, 0, 0, 0, -1, 1, -1).
%F a(n) = 2*A038197(n-2).
%F a(n)=2*a(n-3)+3*a(n-6)-a(n-9)-a(n-12) - Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Jan 12 2003
%F G.f.: -2*x^2*(x^5-2*x^4+2*x^3-x^2-1)/((x^2-x+1)*(x^9-3*x^3+1)). - _Colin Barker_, Nov 09 2012
%Y Cf. A038197.
%K easy,nonn
%O 2,1
%A _Jason Earls_, May 01 2001
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