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 A220571 Composite numbers that are Brazilian. 12
 8, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS There are just two differences of members with A080257: 1) the term 6 is missing here because 6 is not a Brazilian number. 2) the new term 121 is present although 121 has only 3 divisors, because 121 = 11^2 = 11111_3 is a composite number which is Brazilian. 121 is the lone square of a prime which is Brazilian: Theorem 5, page 37 of Quadrature article in links. There is an infinity of Brazilian composite numbers (Theorem 1, page 32 of Quadrature article in links: every even number >= 8 is a Brazilian number). LINKS Michael De Vlieger, Table of n, a(n) for n = 1..10000 Bernard Schott, Les nombres brésiliens, Quadrature, no. 76, avril-juin 2010, pages 30-38; included here with permission from the editors of Quadrature. MATHEMATICA Select[Range[4, 10^2], And[CompositeQ@ #, Module[{b = 2, n = #}, While[And[b < n - 1, Length@ Union@ IntegerDigits[n, b] > 1], b++]; b < n - 1]] &] (* Michael De Vlieger, Jul 30 2017, after T. D. Noe at A125134 *) CROSSREFS Cf. A125134, A190300. Sequence in context: A046031 A102758 A176815 * A033872 A080752 A262159 Adjacent sequences:  A220568 A220569 A220570 * A220572 A220573 A220574 KEYWORD nonn AUTHOR Bernard Schott, Dec 16 2012 STATUS approved

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Last modified February 24 07:19 EST 2020. Contains 332199 sequences. (Running on oeis4.)