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 A060940 #23 Feb 16 2025 08:32:44 %S A060940 2,3,7,5,5,7,11,7,13,19,7,11,29,23,17,11,19,13,17,11,13,23,19,11,13, %T A060940 23,43,17,11,13,17,19,23,13,47,37,71,17,29,19,31,43,13,17,19,23,53,41, %U A060940 29,17,31,19,59,47,61,23,37,103,29,17,19,23,53,41,31,17,19,37,23,41,43,29 %N A060940 Triangle in which n-th row gives the phi(n) terms appearing as initial primes in arithmetic progressions with difference n, with initial term equal to the smallest positive residue coprimes to n. %H A060940 Seiichi Manyama, <a href="/A060940/b060940.txt">Rows n = 1..200, flattened</a> %H A060940 Eric Weisstein's MathWorld, <a href="https://mathworld.wolfram.com/DirichletsTheorem.html">Dirichlet's theorem</a> %H A060940 Wikipedia, <a href="http://en.wikipedia.org/wiki/Dirichlet%27s_theorem_on_arithmetic_progressions">Dirichlet's theorem on arithmetic progressions</a> %e A060940 For differences 1, 2, 3, 4, 5, 6, 7, .. the initial primes are 2; 3; 7, 5; 5, 7; 11, 7, 13, 19; 7, 11; 29, 23, 17, 11, 19, 13; ... etc. Suitable initial values (coprimes to difference) are in A038566. Position of end(start) of rows is given by values of A002088. %e A060940 From _Seiichi Manyama_, Apr 02 2018: (Start) %e A060940 n | phi(n)| %e A060940 ---+-------+------------------------ %e A060940 1 | 1 | 2; %e A060940 2 | 1 | 3; %e A060940 3 | 2 | 7, 5; %e A060940 4 | 2 | 5, 7; %e A060940 5 | 4 | 11, 7, 13, 19; %e A060940 6 | 2 | 7, 11; %e A060940 7 | 6 | 29, 23, 17, 11, 19, 13; %e A060940 8 | 4 | 17, 11, 13, 23; %e A060940 9 | 6 | 19, 11, 13, 23, 43, 17; %e A060940 10 | 4 | 11, 13, 17, 19; (End) %Y A060940 Cf. A000010 (phi), A002088, A038566, A034693, A034694, A002144, A007519, A088732, etc.. %K A060940 nonn,tabf %O A060940 1,1 %A A060940 _Labos Elemer_, May 07 2001