A067194 - OEIS

%I #12 Dec 25 2021 11:34:14

%S 23,61,163,521,821,1297,1861,4201,9049,9631,12391,14437,16987,92767,

%T 94273,96979,108061,123031,125329,127291,142771,148249,165901,180289,

%U 270131,906421,906727,906751,921931,942013,942691,965443,969407,986641

%N Sequence of prime numbers whose reverse is a nontrivial prime power (A025475).

%H Chai Wah Wu, <a href="/A067194/b067194.txt">Table of n, a(n) for n = 1..16435</a>

%e 23 is a prime and its reversal is 32 = 2^5.

%t a = {}; Do[ If[ PrimeQ[n], b = ToExpression[ StringReverse[ ToString[n]]]; If[ !PrimeQ[b] && Mod[b, b - EulerPhi[b]] == 0, a = Append[a, n]]], {n, 1, 10^6} ]; a

%t Select[Prime[Range[80000]],PrimePowerQ[IntegerReverse[#]]&& CompositeQ[ IntegerReverse[ #]]&] (* _Harvey P. Dale_, Dec 25 2021 *)

%o (PARI) lista(nn) = {forprime(p=2, nn, if (ispower(subst(Polrev(digits(p)), x, 10),,&pp) && isprime(pp), print1(p, ", ")););} \\ _Michel Marcus_, Jun 03 2016

%Y Cf. A025475, A007488, A069798.

%K nonn,base

%O 1,1

%A _Shyam Sunder Gupta_, Feb 19 2002

%E Edited and extended by _Robert G. Wilson v_, Feb 19 2002 and Feb 24 2002