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 A340260 #11 Jul 08 2023 20:15:33
%S A340260 1,1,2,1,1,2,1,2,2,3,1,1,2,2,3,1,2,3,4,4,5,1,1,1,2,3,3,4,1,2,3,4,5,6,
%T A340260 6,7,1,1,2,2,3,4,5,5,6,1,2,2,3,4,5,6,7,7,8,1,1,2,3,3,4,5,6,7,7,8,1,2,
%U A340260 3,4,5,6,7,8,9,10,10,11,1,1,1,1,2,2,3,4,5,6,7,7,8
%N A340260 T(n, k) = Sum_{j=1..k} [n mod j <> 1], where [] is the Iverson bracket. Table read by rows.
%e A340260 Table starts:
%e A340260 [1] 1;
%e A340260 [2] 1, 2;
%e A340260 [3] 1, 1, 2;
%e A340260 [4] 1, 2, 2, 3;
%e A340260 [5] 1, 1, 2, 2, 3;
%e A340260 [6] 1, 2, 3, 4, 4, 5;
%e A340260 [7] 1, 1, 1, 2, 3, 3, 4;
%e A340260 [8] 1, 2, 3, 4, 5, 6, 6, 7;
%e A340260 [9] 1, 1, 2, 2, 3, 4, 5, 5, 6;
%e A340260 [10] 1, 2, 2, 3, 4, 5, 6, 7, 7, 8.
%p A340260 IversonBrackets := expr -> subs(true=1, false=0, evalb(expr)):
%p A340260 T := (n, k) -> add(IversonBrackets(irem(n, j) <> 1), j = 1..k):
%p A340260 for n from 1 to 19 do seq(T(n, k), k = 1..n) od;
%Y A340260 T(n, n) = n + 1 - tau(n-1) for n >= 2.
%Y A340260 Cf. A000005, A051731, A243987, A340261.
%K A340260 nonn,tabl
%O A340260 1,3
%A A340260 _Peter Luschny_, Jan 02 2021