A180006 Composite numbers that can be obtained from primes by interchanging the first and last digits.

91, 32, 92, 14, 34, 74, 35, 95, 16, 76, 38, 98, 301, 901, 721, 731, 931, 361, 371, 391, 791, 112, 322, 722, 922, 332, 932, 142, 152, 752, 362, 962, 172, 772, 182, 382, 392, 703, 713, 133, 943, 763, 973, 793, 104, 904, 914, 124, 134, 334, 934, 344, 944, 754

Offset

1,1

Comments

The primes must contain at least two digits.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

The composite number 752 is obtained from the prime 257 by interchanging the first and last digits.

Mathematica

Select[With[{idn=IntegerDigits[#]}, FromDigits[Join[{idn[[-1]]}, Most[Rest[idn]], {idn[[1]]}]]]&/@Prime[Range[5, 1500]], CompositeQ] (* Harvey P. Dale, Jan 26 2025 *)

Crossrefs

The corresponding primes are A076056. Cf. A002808, A179826.

Sequence in context: A119656 A368238 A339141 * A259085 A033411 A329915

Adjacent sequences: A180003 A180004 A180005 * A180007 A180008 A180009

Keyword

nonn,base

Author

Parthasarathy Nambi, Aug 06 2010

Extensions

More terms from Vincenzo Librandi, Aug 06 2010

Status

approved