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A073418
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Useless numbers: numbers written in English without any of the letters e, s or u.
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0
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2, 30, 32, 40, 42, 50, 52, 2000000, 2000002, 2000030, 2000032, 2000040, 2000042, 2000050, 2000052, 30000000, 30000002, 30000030, 30000032, 30000040, 30000042, 30000050, 30000052, 32000000, 32000002, 32000030, 32000032, 32000040, 32000042, 32000050, 32000052
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OFFSET
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1,1
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COMMENTS
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After a(7), the sequence contains only terms of the form a(i) * 10^(3*k) and a(i) * 10^(3*k) + a(j) for 1 <= i, j <= 7, where the name of 10^(3*k) is useless, e.g., 10^6 (million), 10^9 (billion), 10^12 (trillion), 10^27 (octillion), 10^30 (nonillion), ... (see links for large number names). - Michael S. Branicky, Jan 01 2021
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LINKS
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Table of n, a(n) for n=1..31.
M. J. Halm, Sequences (Re)discovered, Mpossibilities 81 (Aug. 2002).
Eric Weisstein's World of Mathematics, Large Number
Wikipedia, Names of Large Numbers
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EXAMPLE
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a(2) = 30 because 30 is the second integer without an e, s or u in its English name.
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CROSSREFS
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Sequence in context: A228937 A071056 A075716 * A022377 A145290 A343930
Adjacent sequences: A073415 A073416 A073417 * A073419 A073420 A073421
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KEYWORD
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nonn,word
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AUTHOR
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Michael Joseph Halm, Aug 23 2002
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EXTENSIONS
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Removed 'ninety' and 'ninety two' from the sequence which clearly include the letter E. Likewise removed 'two hundrEd' and others. Inserted 'thirty' and 'thirty-two'. - Freddie Noble, Jan 01 2021
a(16)-a(31) from Michael S. Branicky, Jan 01 2021
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STATUS
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approved
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