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 A374451 #6 Jul 13 2024 07:45:34
%S A374451 2,3,2,2,2,2,5,2,3,2,2,3,2,2,2,7,2,3,2,5,2,2,2,2,2,2,2,2,3,2,3,2,3,2,
%T A374451 3,2,2,5,2,2,2,3,2,2,2,11,2,3,2,5,2,7,2,3,2,2,2,2,3,2,2,2,2,2,2,2,13,
%U A374451 2,3,2,5,2,7,2,3,2,11,2,2,7,2,2,2,3,2,2,2,5,2,2,2
%N A374451 Triangle T(n, k), n > 1, k = 1..n-1, read by rows; T(n, k) is the least prime number p such that the p-adic valuations of n and k differ.
%F A374451 T(n, 1) = A020639(n).
%F A374451 T(n, n-1) = 2.
%F A374451 T(2^n, k) = 2.
%F A374451 T(p, k) = A020639(k) for any prime number p and k > 1.
%e A374451 Triangle T(n, k) begins:
%e A374451 n n-th row
%e A374451 -- -------------------------------
%e A374451 2 2
%e A374451 3 3, 2
%e A374451 4 2, 2, 2
%e A374451 5 5, 2, 3, 2
%e A374451 6 2, 3, 2, 2, 2
%e A374451 7 7, 2, 3, 2, 5, 2
%e A374451 8 2, 2, 2, 2, 2, 2, 2
%e A374451 9 3, 2, 3, 2, 3, 2, 3, 2
%e A374451 10 2, 5, 2, 2, 2, 3, 2, 2, 2
%e A374451 11 11, 2, 3, 2, 5, 2, 7, 2, 3, 2
%e A374451 12 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2
%o A374451 (PARI) T(n, k) = { forprime (p = 2, oo, my (d = valuation(n, p) - valuation(k, p)); if (d, return (p););); }
%Y A374451 Cf. A020639, A374369.
%K A374451 nonn,easy,tabl
%O A374451 2,1
%A A374451 _Rémy Sigrist_, Jul 08 2024