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 A249716 #12 Nov 05 2014 11:22:02 %S A249716 1,1,1,1,4,1,20,1,8,9,45,1,12,1287,364,6435,16,136,18,171,20,5985, %T A249716 1540,1,24,25,325,27,28,3654,4060,169911,32,528,5984,52360,36,666, %U A249716 8436,82251,40,820,11480,145008513,44,45,1035,12551759587422,48,49,50,1275,52,292825,54,1485,56,1596,30856,45057474,60,55525372,37820,63,64,2080 %N A249716 The least nonsquarefree number on row n of Pascal's triangle, or 1 if all the terms on that row are squarefree. %C A249716 After a(0) = 1, A048278 gives the positions of seven other ones in the sequence. %H A249716 Antti Karttunen, <a href="/A249716/b249716.txt">Table of n, a(n) for n = 0..10000</a> %F A249716 a(n) = binomial(n, A249442(n)). %e A249716 Binomial coefficients First squarefree a(n) %e A249716 A007318 occurs at index? = %e A249716 ---------------------------------------------------------------------------- %e A249716 Row 0 1 no squarefrees 1 (by definition) %e A249716 Row 1 1 1 no squarefrees 1 %e A249716 Row 2 1 2 1 no squarefrees 1 %e A249716 Row 3 1 3 3 1 no squarefrees 1 %e A249716 Row 4 1 4 6 4 1 1 4 %e A249716 Row 5 1 5 10 10 5 1 no squarefrees 1 %e A249716 Row 6 1 6 15 20 15 6 1 3 20 %o A249716 (PARI) %o A249716 A249716(n) = { my(b); for(k=0,n\2,if(0==moebius(b=binomial(n,k)),return(b))); return(1); } %o A249716 for(n=0, 10000, write("b249716.txt", n, " ", A249716(n))); %o A249716 (Scheme) (define (A249716 n) (A007318tr n (A249442 n))) %Y A249716 A249717 and A249718 give the smallest and the largest prime whose square divides these numbers. %Y A249716 Cf. also A007318, A005117, A013929, A048277, A048278, A249442. %K A249716 nonn %O A249716 0,5 %A A249716 _Antti Karttunen_, Nov 04 2014