A242835 - OEIS

%I #28 Oct 29 2020 18:53:38

%S 2,223,22360679774997896964091

%N Primes formed by the initial digits of the decimal expansion of the square root of 5.

%C There is no other term with less than 111 digits.

%C a(4) has 1506 digits. - _Hiroaki Yamanouchi_, Sep 11 2014

%e Decimal expansion of sqrt(5) begins: 2.23606797749978969640917366... - _Wesley Ivan Hurt_, May 26 2014

%t Module[{d=25,f},f=RealDigits[Sqrt[5],10,d][[1]];Select[ Table[ FromDigits[ Take[f,n]],{n,d}],PrimeQ]] (* _Harvey P. Dale_, Oct 29 2020 *)

%Y Cf. A005042, A007512, A072952, A119343.

%Y Cf. A002163 (Decimal Expansion of sqrt(5)).

%K nonn,base,bref

%O 1,1

%A _Felix Fröhlich_, May 23 2014