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 A280426 #12 Jan 06 2017 10:56:01 %S A280426 0,0,0,1,1,2,4,8,6,2,2,9,1,5,8,5,1,1,6,4,3,5,9,3,2,1,6,3,3,4,7,8,4,5, %T A280426 6,5,2,9,4,2,8,5,1,7,3,7,9,8,9,6,5,1,3,6,6,7,4,5,4,2,6,8,2,9,7,8,8,5, %U A280426 1,4,9,1,6,2,9,9,8,1,9,9,9,1,1,2,4,8,6,2 %N A280426 Digital roots of tetranacci numbers A000078. %C A280426 From a(3) onwards, periodic with period length 78, twice the periodicity of the digital roots of tribonacci numbers A222407 (also the 12th triangular number). %F A280426 a(n) = A010888(A000078(n)). %Y A280426 Cf. A000078, A010888, A222407. %K A280426 nonn,base %O A280426 0,6 %A A280426 _Peter M. Chema_, Jan 02 2017