A163117 The pairs of central digits of all primes with an even number of digits.

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

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