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%I A095180 #28 Feb 12 2024 01:53:07
%S A095180 2,3,5,7,11,31,71,13,73,17,37,97,79,101,701,311,131,941,151,751,761,
%T A095180 971,181,191,991,113,313,733,743,353,953,373,383,983,107,907,727,337,
%U A095180 937,347,157,757,167,967,787,797,709,919,929,739,149,359,769,179,389,199
%N A095180 Reverse digits of primes, append to sequence if result is a prime.
%C A095180 Conjecture: the Benford law limit is 2=Sum[N[Log[10, 1 + 1/d[[n]]]], {n, 1, Length[d]}]^2/(( #totalprimes/#totalPrimes)). At 50000 primes total it is 2.05931. - _Roger L. Bagula_ and _Gary W. Adamson_, Jul 02 2008
%C A095180 Presumably this does not satisfy Benford's law. - _N. J. A. Sloane_, Feb 09 2017
%H A095180 Indranil Ghosh, <a href="/A095180/b095180.txt">Table of n, a(n) for n = 1..25000</a> (terms 1..206 from Roger L. Bagula and Gary W. Adamson)
%H A095180 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/BenfordsLaw.html">Benford's Law</a>.
%H A095180 <a href="/index/Be#Benford">Index entries for sequences related to Benford's law</a>
%e A095180 The prime 107 in reverse is 701 which is prime.
%t A095180 b = Flatten[Table[If[PrimeQ[Sum[IntegerDigits[Prime[n]][[i]]*10^(i - 1), {i, 1, Length[IntegerDigits[Prime[n]]]}]], Sum[IntegerDigits[Prime[n]][[i]]*10^(i - 1), {i, 1, Length[IntegerDigits[Prime[n]]]}], {}], {n, 1,1000}]] (* _Roger L. Bagula_ and _Gary W. Adamson_, Jul 02 2008 *)
%t A095180 Select[FromDigits[Reverse[IntegerDigits[#]]]&/@Prime[Range[300]],PrimeQ] (* _Harvey P. Dale_, May 05 2015 *)
%o A095180 (PARI) r(n) = forprime(x=1,n,y=eval(rev(x));if(isprime(y),print1(y","))) \ Get the reverse of the input string rev(str) = { local(tmp,j,s); tmp = Vec(Str(str)); s=""; forstep(j=length(tmp),1,-1, s=concat(s,tmp[j])); return(s) }
%o A095180 (Haskell)
%o A095180 a095180 n = a095180_list !! (n-1)
%o A095180 a095180_list =filter ((== 1) . a010051) a004087_list
%o A095180 -- _Reinhard Zumkeller_, Oct 14 2011
%Y A095180 Cf. A007500.
%Y A095180 Cf. A004087, A010051.
%K A095180 base,easy,nonn
%O A095180 1,1
%A A095180 _Cino Hilliard_, Jun 21 2004

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