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 A241019 Let x(1)x(2)... x(n) denote the decimal expansion of a number p having an index j such that x(j) = 1 and x(i) = 3 for i <> j.  The sequence lists the smallest index j such that p is prime, or 0 if no such prime exists. 5
 1, 2, 3, 2, 2, 4, 2, 6, 5, 5, 5, 0, 3, 8, 1, 11, 7, 6, 4, 5, 11, 5, 0, 0, 9, 11, 0, 5, 5, 0, 4, 5, 17, 19, 19, 6, 0, 3, 9, 35, 1, 27, 24, 32, 0, 36, 14, 11, 34, 14, 22, 0, 17, 53, 0, 47, 11, 0, 16, 3, 0, 15, 0, 39, 22, 40, 27, 39, 0, 19, 2, 19, 48, 2, 43, 19 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Except 0, the corresponding primes are 13, 313, 3313, 31333, 313333, 3331333, 31333333, 333331333, 3333133333, 33331333333, 333313333333, 0, 33133333333333, ... . LINKS MAPLE with(numtheory):nn:=80:T:=array(1..nn):    for n from 2 to nn do:      for i from 1 to n do:      T[i]:=3:      od:        ii:=0:        for j from 1 to n while(ii=0)do:        T[j]:=1:s:=sum('T[i]*10^(n-i)', 'i'=1..n):          if type(s, prime)=true          then          ii:=1: printf(`%d, `, j):          else          T[j]:=3:          fi:          od:           if ii=0            then            printf(`%d, `, 0):            else           fi:        od: CROSSREFS Cf. A241018, A241020. Sequence in context: A295312 A212174 A160558 * A023581 A023574 A210941 Adjacent sequences:  A241016 A241017 A241018 * A241020 A241021 A241022 KEYWORD nonn,base AUTHOR Michel Lagneau, Apr 15 2014 STATUS approved

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Last modified August 8 02:45 EDT 2020. Contains 336290 sequences. (Running on oeis4.)