A287294 Concatenation of sequence (2n-1,2n-3,..,3,1,3,..,2n-3,2n-1).

1, 313, 53135, 7531357, 975313579, 1197531357911, 13119753135791113, 151311975313579111315, 1715131197531357911131517, 19171513119753135791113151719, 211917151311975313579111315171921, 2321191715131197531357911131517192123

Offset

1,2

Comments

For n <= 1400, a(2) = 313, a(10) = 19171513119753135791113151719, a(12) = 2321191715131197531357911131517192123 and a(110) = 219217..313..217219 are primes.

Links

Table of n, a(n) for n=1..12.

F. Smarandache, Sequences of Numbers Involved in Unsolved Problems.

Eric Weisstein's World of Mathematics, Smarandache Sequences

Mathematica

Block[{nn = 12, s}, s = IntegerDigits@ Range[1, 2 nn - 1, 2]; Table[FromDigits@ Flatten@ Join[Reverse[Rest@ #], #] &@ Take[s, n], {n, nn}]] (* Michael De Vlieger, May 23 2017 *)

Crossrefs

Cf. A007942.

Sequence in context: A210071 A327636 A332131 * A255388 A261818 A083997

Adjacent sequences: A287291 A287292 A287293 * A287295 A287296 A287297

Keyword

base,easy,nonn

Author

XU Pingya, May 22 2017

Status

approved