This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A074464 #21 Oct 16 2024 09:19:38 %S A074464 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 A074464 5,4,3,5,4,3,3,5,3,4,5,3,3,5 %N A074464 Average digit (rounded down) in the decimal expansion of a prime number p, where 2^p-1 is a Mersenne prime. %F A074464 a(n) = A004426(A000043(n)). - _Michel Marcus_, Aug 04 2018 %e A074464 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 A074464 Floor[Mean[IntegerDigits[#]]]&/@MersennePrimeExponent[Range[47]] (* _Harvey P. Dale_, Apr 19 2019 *) %Y A074464 Cf. A000043, A004426, A074463. %K A074464 nonn,base,more %O A074464 1,1 %A A074464 Y. Kelly Itakura (yitkr(AT)mta.ca), Aug 23 2002 %E A074464 a(21)-a(47) from _Ivan Panchenko_, Aug 03 2018 %E A074464 a(48) from _Amiram Eldar_, Oct 16 2024