A209620 Emirps that become their own reversals when rotated through 180 degrees (including on calculator display).

1021, 1151, 1181, 1201, 1511, 1811, 10151, 11551, 15101, 15511, 100511, 101281, 102181, 102551, 105211, 105251, 108881, 110051, 110221, 110281, 110881, 111211, 111821, 112111, 112181, 112501, 115001, 115021, 118081, 120121, 120511, 121021, 121151, 122011

Offset

1,1

Comments

Such emirps have end digits 1 and use only digits 0, 1, 2, 5, 8, and the sequence naturally includes A155512, the emirps with only digits 0 and 1.

Links

Table of n, a(n) for n=1..34.

Example

1181 of this sequence, for instance, belongs to the emirp pair (1181, 1811), where each member is a 180-degree rotation of the other; similarly for the term 112501 of this sequence, that belongs to the emirp pair (105211, 112501) and which, displayed on a calculator and turned upside-down, becomes its own reversal.

Mathematica

t1 = {0, 1, 2, 5, 8}; okQ[n_] := Module[{d = IntegerDigits[n], r}, r = Reverse[d];  r != d && Complement[d, t1] == {} && PrimeQ[FromDigits[r]]]; Select[Prime[Range[100000]], okQ] (* T. D. Noe, Apr 24 2012 *)

Crossrefs

Cf. A006567.

Sequence in context: A356947 A214732 A088290 * A179032 A179033 A082059

Adjacent sequences: A209617 A209618 A209619 * A209621 A209622 A209623

Keyword

nonn,base

Author

Lekraj Beedassy, Mar 21 2012

Status

approved