Mmmmh, as we don't accept integers with leading zeros in S, my start might be wrong... And I fear some backtracking might be necessary too... à+ É. Catapulté de mon aPhone
Le 18 nov. 2019 à 11:51, Éric Angelini <eric.angelini@skynet.be> a écrit :
Hello Math-Fun, S is the lexicographically earliest seq of distinct integers [separated only by a comma, and starting with a(1) = 1] such that the yellow digits appear in the exact same order as the non yellow digits. A yellow digit is a digit in contact with at least one comma of S. Question: For which a(n) will the quantity of yellow digits equal the quantity of non yellow digits [if such an a(n) exists]?
S starts like this, if I am not wrong: S = 1,2,3,4,5,6,78,9,10,11,12,13,...,97,98,99, 110,120,130,140,150,160,170,180,190,111, 100,112,113,114,121,115,131,116,141,117,... (S is perhaps already in the OEIS -- but I could not find it; anyway the question remains). Best, É.
à+ É. Catapulté de mon aPhone
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