A156063 Odd composite numbers whose reversal is a different composite.

15, 21, 25, 27, 39, 45, 49, 51, 57, 63, 65, 69, 75, 81, 85, 87, 93, 105, 115, 117, 123, 129, 135, 143, 147, 153, 155, 159, 165, 169, 177, 183, 185, 187, 189, 195, 201, 203, 205, 207, 209, 213, 215, 217, 219, 221, 225, 231, 235, 237, 243, 245, 247, 249, 253, 255

Offset

1,1

Links

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

Example

If odd composite 15 < 51 = composite, then 15=a(1). If odd composite 21 > 12 = composite, then 21=a(2). If odd composite 25 < 52 = composite, then 25=a(3), etc.

Mathematica

Select[Range[1, 301, 2], AllTrue[{#, IntegerReverse[#]}, CompositeQ]&&#!=IntegerReverse[#]&] (* Harvey P. Dale, May 03 2024 *)

Crossrefs

Cf. A006567, A071904.

Sequence in context: A177024 A325037 A154545 * A181780 A273061 A129926

Adjacent sequences: A156060 A156061 A156062 * A156064 A156065 A156066

Keyword

nonn,base

Author

Juri-Stepan Gerasimov, Feb 03 2009

Extensions

Added missing numbers in the 201-299 range. R. J. Mathar, Feb 13 2009

Status

approved