|
%I #20 Aug 23 2020 02:09:35
%S 1,9,10,11,12,13,14,15,16,17,18,20,36,38,39,40,41,42,43,44,46,66,67,
%T 68,69,70,71,72,73,92,101,121,122,123,124,125,126,127,146,155,174,182,
%U 201,211,229,230,237,256,284,285,286,287,288,289,290,291,311,348,365,368
%N Ulam numbers starting with the numbers 1 and 9.
%D Clifford A. Pickover, Wonders of Numbers, Oxford University Press, NY, 2001, p. 185-186.
%H Amiram Eldar, <a href="/A060009/b060009.txt">Table of n, a(n) for n = 1..10000</a>
%H Clifford A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," <a href="http://www.zentralblatt-math.org/zmath/en/search/?q=an:0983.00008&format=complete">Zentralblatt review</a>.
%F Ulam numbers are positive integers that can be expressed in just one way as the sum of two distinct earlier members of the sequence in increasing order.
%e a(4) = 11 is an Ulam number because 10 + 1 = 11, but 19 is not because there is more than one way to form 19 from summing previous sequence numbers, e.g., 18 + 1 and 10 + 9.
%Y Cf. A002858.
%K nonn,base
%O 1,2
%A _Jason Earls_, Mar 16 2001
|
