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%I #9 Jul 31 2015 20:34:21
%S 9,24,33,48,69,84,93,108,129,144,153,168,189,204,213,228,249,264,273,
%T 288,309,324,333,348,369,384,393,408,429,444,453,468,489,504,513,528,
%U 549,564,573,588,609,624,633,648,669,684,693,708,729,744,753,768,789
%N Numbers m such that (m mod k) > (m+2 mod k) with least value of k = 5.
%C Or, numbers m such A121937(m)=5. Cf. A121937 a(n) = least m >= 2 such that (n mod m) > (n+2 mod m).
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2, -2, 2, -1).
%F a(n) = 3*(sin((n*Pi)/2)- cos((n*Pi)/2)+5*n-3).
%F a(1)=9, a(2)=24, a(3)=33, a(4)=48, a(n)=2*a(n-1)-2*a(n-2)+2*a(n-3)-a(n-4). Empirical G.f.: 3*x*(3+2*x+x^2+4*x^3)/(1-2*x+2*x^2-2*x^3+x^4). [Colin Barker, Jan 25 2012]
%e 9 is here because least k such that (9 mod k) > (11 mod k) is 5;
%e 24 is here because least k such that (24 mod k) > (26 mod k) is 5.
%t Table[15*n-9-3*Cos[(n*Pi)/2]+3*Sin[(n*Pi)/2],{n,60}]
%t LinearRecurrence[{2,-2,2,-1},{9,24,33,48},60] (* _Harvey P. Dale_, Mar 28 2013 *)
%Y Cf. A121937.
%K nonn
%O 1,1
%A _Zak Seidov_, Sep 07 2006