A171807 - OEIS

A171807

Emirps (A006567) p such that R(prime(p)) is prime.

37, 71, 157, 167, 199, 907, 953, 971, 991, 1151, 1193, 1213, 1223, 1231, 1237, 1279, 1283, 1381, 1429, 1471, 1499, 1523, 1583, 1597, 1601, 1619, 1669, 1811, 1831, 1867, 3299, 3343, 3347, 3371, 3373, 3391, 3463, 3467, 3469, 3527, 3541, 3719, 3767, 3803

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..44.

FORMULA

{n such that n is in A000040 and A006567(n) is in A000040 and A000040(n) is in A000040 and A006567(A000040(n)) is in A000040}.

EXAMPLE

a(1) = 37 because 37 and R(37) = 73 are prime, as are prime(37) = 157 and R(prime(37)) = 751. a(2) = 71 because 71 and R(71) = 17 are prime, as are prime(71) = R(prime(71)) = 353 (which is not an emirp because the reversal is the same prime). a(3) = 157 because 157 and R(157) = 751 are prime, as are prime(157) = R(prime(157)) = 919 (which is not an emirp because the reversal is the same prime). a(4) = 167 because 167 and R(157) = 671 are prime, as are prime(167) = 991 and R(prime(167)) = 199. a(5) = 199 because 199 and (199) = 991 are prime, as are prime(199) = 1217 and R(1217)= prime(912) = 7121.

MATHEMATICA

emQ[n_]:=Module[{idn=IntegerDigits[n], revidn}, revidn=Reverse[idn]; idn!= revidn && PrimeQ[FromDigits[revidn]] && PrimeQ[FromDigits[ Reverse[ IntegerDigits[ Prime[n]]]]]]; Select[Prime[Range[600]], emQ] (* Harvey P. Dale, Mar 01 2012 *)

CROSSREFS

Cf. A000040, A004086, A006567.

Sequence in context: A138396 A335484 A155087 * A178399 A044103 A044484

Adjacent sequences: A171804 A171805 A171806 * A171808 A171809 A171810

KEYWORD

easy,nonn,less,base

AUTHOR

Jonathan Vos Post, Dec 18 2009

EXTENSIONS

More terms from R. J. Mathar, Jan 25 2010

STATUS

approved