A074464 - OEIS

%I #21 Oct 16 2024 09:19:38

%S 2,3,5,7,2,4,5,2,3,8,2,3,2,4,4,1,3,3,3,3,8,5,1,5,2,3,5,4,1,3,3,6,5,5,

%T 5,4,3,5,4,3,3,5,3,4,5,3,3,5

%N Average digit (rounded down) in the decimal expansion of a prime number p, where 2^p-1 is a Mersenne prime.

%F a(n) = A004426(A000043(n)). - _Michel Marcus_, Aug 04 2018

%e Prime numbers for Mersenne are 2, 3, 5, 7, 13, 17, 19, 31, 61, ..., so the averages of digits rounded down are 2, 3, 5, 7, (1+3)/2 = 2, (1+7)/2 = 4, (1+9)/2 = 5, (3+1)/2 = 2, floor((6+1)/2) = 3, ...

%t Floor[Mean[IntegerDigits[#]]]&/@MersennePrimeExponent[Range[47]] (* _Harvey P. Dale_, Apr 19 2019 *)

%Y Cf. A000043, A004426, A074463.

%K nonn,base,more

%O 1,1

%A Y. Kelly Itakura (yitkr(AT)mta.ca), Aug 23 2002

%E a(21)-a(47) from _Ivan Panchenko_, Aug 03 2018

%E a(48) from _Amiram Eldar_, Oct 16 2024