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 A072957 Urban numbers: without 'r' or 'u'. 4
 1, 2, 5, 6, 7, 8, 9, 10, 11, 12, 15, 16, 17, 18, 19, 20, 21, 22, 25, 26, 27, 28, 29, 50, 51, 55, 56, 57, 58, 59, 60, 61, 62, 65, 66, 67, 68, 69, 70, 71, 72, 75, 76, 77, 78, 79, 80, 81, 82, 85, 86, 87, 88, 89, 90, 91, 92, 95, 96, 97, 98, 99, 1000000, 1000001, 1000002 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES M. J. Halm, Sequences (Re)discovered, Mpossibilities 81 (Aug. 2002). LINKS PROG (PARI) is(n)=!setintersect(Set(Vec(English(n))), ["r", "u"]) \\ See A052360 for English(). - M. F. Hasler, Apr 01 2019 /* Alternate code, not using English(): (valid for 1 <= n < one trillion, which should be forbidden due to the 'r' but returns 1) */ is(n)={setintersect( Set(digits(n)), [3, 4]) && return; !while(n=divrem(n, 10^6), n[2]<100||return; n=n[1])} \\ M. F. Hasler, Apr 01 2019 CROSSREFS Cf. A006933 (eban numbers: without 'e'), A008521 (without 'o'), A008523 (without 't'), A008537 (without 'n'), A089590 (without 'u'), A072956 (turban numbers: without r, t or u), A089589 (without 'i'). Sequence in context: A039239 A039182 A039135 * A073416 A138100 A039097 Adjacent sequences:  A072954 A072955 A072956 * A072958 A072959 A072960 KEYWORD easy,nonn,word AUTHOR Michael Joseph Halm, Aug 13 2002 STATUS approved

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Last modified August 19 18:51 EDT 2019. Contains 326133 sequences. (Running on oeis4.)