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a(n) = ceiling(24(2^n-1)/n).
3

%I #10 Mar 25 2017 09:39:38

%S 24,36,56,90,149,252,436,765,1363,2456,4467,8190,15122,28086,52428,

%T 98303,185042,349524,662258,1258290,2396744,4575604,8753330,16777215,

%U 32212254,61946643,119304647,230087533

%N a(n) = ceiling(24(2^n-1)/n).

%H R. J. Penrose, <a href="http://people.maths.ox.ac.uk/lmason/Tn/TN1-25/No10%202%20July%201980.pdf">Puzzle</a>, Twistor Newsletter, No. 10 (July 1980), p. 22.

%H R. J. Penrose, <a href="/A003138/a003138.pdf">Puzzle</a>, Twistor Newsletter, No. 10 (July 1980), p. 22. [Cached copy]

%H R. J. Penrose, <a href="http://people.maths.ox.ac.uk/lmason/Tn/41/TN41.pdf">Solution to puzzle</a>, Twistor Newsletter, No. 41, p. 37, 1996.

%H R. J. Penrose, <a href="/A003138/a003138_1.pdf">Solution to puzzle</a>, Twistor Newsletter, No. 41, p. 37, 1996. [Cached copy]

%Y Cf. A003176, A003138, A121056.

%K nonn

%O 1,1

%A _N. J. A. Sloane_