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Search: id:A060009
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| A060009 |
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Ulam numbers with starting with 1 and 9. |
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+0
1
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| 1, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 36, 38, 39, 40, 41, 42, 43, 44, 46, 66, 67, 68, 69, 70, 71, 72, 73, 92, 101, 121, 122, 123, 124, 125, 126, 127, 146, 155, 174, 182, 201, 211, 229, 230, 237, 256, 284, 285, 286, 287, 288, 289, 290, 291, 311, 348, 365, 368
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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C. Pickover, Wonders of Numbers, Oxford University Press, NY, 2001, p. 185-186.
Cf. A002858
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LINKS
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C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," Zentralblatt review
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FORMULA
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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.
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EXAMPLE
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a(4)=11 is an Ulam number because 10 + 1 = 11, but 19 isn't because there is more than one way to form 19 from summing previous sequence numbers, e.g. 18 + 1, and 10 + 9.
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CROSSREFS
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Cf. A002858.
Sequence in context: A020723 A107043 A023392 this_sequence A115843 A058365 A121816
Adjacent sequences: A060006 A060007 A060008 this_sequence A060010 A060011 A060012
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KEYWORD
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nonn
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AUTHOR
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Jason Earls (jcearls(AT)cableone.net), Mar 16 2001
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