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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 Harvey P. Dale, Table of n, a(n) for n = 1..2000 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 Cf. A093339, A162908. Sequence in context: A194181 A277934 A063754 * A099749 A210442 A077202 Adjacent sequences: A163114 A163115 A163116 * A163118 A163119 A163120 KEYWORD nonn,base,less AUTHOR Juri-Stepan Gerasimov, Jul 21 2009 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.)