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

Offset: 1

Author

Jonathan Vos Post, Dec 18 2009

Keywords

• easy
• nonn
• less
• base

Examples

			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.
		

Crossrefs

Cf. A000040, A004086, A006567.

Programs

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 *)

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}.

Extensions

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