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 A262581 Concatenation of the numbers from 1 to n but omitting 11. 1
 1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678910, 1234567891012, 123456789101213, 12345678910121314, 1234567891012131415, 123456789101213141516, 12345678910121314151617, 1234567891012131415161718, 123456789101213141516171819, 12345678910121314151617181920 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS There are only two primes among the first 98 terms, namely 123456789101213 and 1234567891012131415161718192021222324252627282930313233343536\ 373839404142434445464748495051525354555657585960616263. Does this sequence contain any other primes? No other primes through a(10000). - Robert Price, Nov 05 2018 LINKS MATHEMATICA DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {11}]]]], {n, 20}]] (* Robert Price, Nov 05 2018 *) PROG (PARI) terms(n) = my(s="", i=0); for(k=1, n, if(k!=11, s=concat(s, Str(k)); print1(eval(s), ", "); i++); if(i==n, break)) /* Print initial 20 terms as follows */ terms(20) \\ Felix FrÃ¶hlich, Nov 05 2018 CROSSREFS Cf. A007908, A262299, A262571-A262582. See A262300 for more about this problem. Sequence in context: A138957 A007908 A262582 * A262580 A262579 A057932 Adjacent sequences:  A262578 A262579 A262580 * A262582 A262583 A262584 KEYWORD nonn,base AUTHOR N. J. A. Sloane, Sep 25 2015 STATUS approved

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Last modified March 30 06:59 EDT 2020. Contains 333119 sequences. (Running on oeis4.)