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A163117 The pairs of central digits of all primes with an even number of digits. 2
1, 1, 1, 3, 1, 7, 1, 9, 2, 3, 2, 9, 3, 1, 3, 7, 4, 1, 4, 3, 4, 7, 5, 3, 5, 9, 6, 1, 6, 7, 7, 1, 7, 3, 7, 9, 8, 3, 8, 9, 9, 7, 0, 0, 0, 1, 0, 1, 0, 2, 0, 3, 0, 3, 0, 3, 0, 4, 0, 5, 0, 6, 0, 6, 0, 6, 0, 8, 0, 9, 0, 9, 0, 9, 1, 0, 1, 0, 1, 1, 1, 2, 1, 2, 1, 5, 1, 5, 1, 6, 1, 7, 1, 8, 1, 8, 1, 9, 2, 0, 2, 1, 2, 1, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
A subsequence of A033308.
LINKS
EXAMPLE
a(1)=1 and a(2)=1 represent the two digits of 11.
a(7)=1 and a(8)=9 represent the two digits of 19.
a(43)=0 and a(44)=0 represent the two zeros of the prime 1009.
MATHEMATICA
cd[n_]:=Module[{idn=IntegerDigits[n], len}, len=IntegerLength[n]/2; Take[ idn, {len, len+1}]]; cd/@Select[Prime[Range[200]], EvenQ[ IntegerLength[ #]]&]//Flatten (* Harvey P. Dale, Jul 23 2018 *)
CROSSREFS
Sequence in context: A194181 A277934 A063754 * A099749 A210442 A077202
KEYWORD
nonn,base,less
AUTHOR
EXTENSIONS
a(8) corrected by R. J. Mathar, Jul 27 2009
STATUS
approved

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Last modified April 18 16:22 EDT 2024. Contains 371780 sequences. (Running on oeis4.)