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A288291
Position of the first time an n-digit number appears twice in a row after the decimal point of e.
2
31, 49, 97, 2, 112869, 5005575, 1561314, 69682897, 1841794338
OFFSET
1,1
COMMENTS
18281828 appears in e before any 1-digit, 2-digit, or 3-digit number appears twice in a row.
EXAMPLE
a(1) = 31 because the first time a 1-digit number appears twice in a row in the decimal expansion of e is 31 digits after the decimal point: 2.718281828459045235360287471352(66)...
MATHEMATICA
s = First@ RealDigits[E, 10, 51*^5]; Table[p = Partition[s, k, 1];
SelectFirst[ Range[ Length[p] - k], p[[#]] == p[[# + k]] &] - 1, {k, 7}] (* Giovanni Resta, Sep 05 2017 *)
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Bobby Jacobs, Sep 01 2017
EXTENSIONS
a(6)-a(8) from Giovanni Resta, Sep 05 2017
a(9) from Michael S. Branicky, Jan 20 2023
STATUS
approved