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 A140271 #29 Apr 08 2021 08:23:13 %S A140271 1,2,3,4,5,3,7,4,9,5,11,4,13,7,5,8,17,6,19,5,7,11,23,6,25,13,9,7,29,6, %T A140271 31,8,11,17,7,9,37,19,13,8,41,7,43,11,9,23,47,8,49,10,17,13,53,9,11,8, %U A140271 19,29,59,10,61,31,9,16,13,11,67,17,23,10,71,9,73,37,15,19,11,13,79,10,27 %N A140271 Least divisor of n that is > sqrt(n), with a(1) = 1. %C A140271 If n is not a square, then a(n) = A033677(n). %C A140271 If we define a divisor d|n to be strictly superior if d > n/d, then strictly superior divisors are counted by A056924 and listed by A341673. This sequence selects the smallest strictly superior divisor of n. - _Gus Wiseman_, Apr 06 2021 %H A140271 Alois P. Heinz, <a href="/A140271/b140271.txt">Table of n, a(n) for n = 1..10000</a> %e A140271 From _Gus Wiseman_, Apr 06 2021: (Start) %e A140271 a(n) is the smallest element in the following sets of strictly superior divisors: %e A140271 1: {1} 16: {8,16} 31: {31} %e A140271 2: {2} 17: {17} 32: {8,16,32} %e A140271 3: {3} 18: {6,9,18} 33: {11,33} %e A140271 4: {4} 19: {19} 34: {17,34} %e A140271 5: {5} 20: {5,10,20} 35: {7,35} %e A140271 6: {3,6} 21: {7,21} 36: {9,12,18,36} %e A140271 7: {7} 22: {11,22} 37: {37} %e A140271 8: {4,8} 23: {23} 38: {19,38} %e A140271 9: {9} 24: {6,8,12,24} 39: {13,39} %e A140271 10: {5,10} 25: {25} 40: {8,10,20,40} %e A140271 11: {11} 26: {13,26} 41: {41} %e A140271 12: {4,6,12} 27: {9,27} 42: {7,14,21,42} %e A140271 13: {13} 28: {7,14,28} 43: {43} %e A140271 14: {7,14} 29: {29} 44: {11,22,44} %e A140271 15: {5,15} 30: {6,10,15,30} 45: {9,15,45} %e A140271 (End) %p A140271 with(numtheory): %p A140271 a:= n-> min(select(d-> is(d=n or d>sqrt(n)), divisors(n))): %p A140271 seq(a(n), n=1..100); # _Alois P. Heinz_, Jan 29 2018 %t A140271 Table[Select[Divisors[n], # > Sqrt[n] &][[1]], {n, 2, 70}] (* _Stefan Steinerberger_, May 18 2008 *) %o A140271 (PARI) A140271(n)={local(d,a);d=divisors(n);a=n;for(i=1,length(d),if(d[i]>sqrt(n),a=min (d[i],a)));a} \\ _Michael B. Porter_, Apr 06 2010 %Y A140271 Cf. A060775, A033676, A033677. %Y A140271 These divisors are counted by A056924. %Y A140271 These divisors add up to A238535. %Y A140271 These divisors that are odd are counted by A341594. %Y A140271 These divisors that are squarefree are counted by A341595 %Y A140271 These divisors that are prime are counted by A341642. %Y A140271 These divisors are listed by A341673. %Y A140271 A038548 counts superior (or inferior) divisors. %Y A140271 A161906 lists inferior divisors. %Y A140271 A161908 lists superior divisors. %Y A140271 A207375 list central divisors. %Y A140271 A341674 lists strictly inferior divisors. %Y A140271 - Inferior: A063962, A066839, A069288, A217581, A333749, A333750. %Y A140271 - Superior: A051283, A059172, A063538, A063539, A070038, A072500, A116882, A116883, A341591, A341592, A341593, A341675, A341676. %Y A140271 - Strictly Inferior: A070039, A333805, A333806, A341596, A341677. %Y A140271 - Strictly Superior: A048098, A064052, A341643, A341644, A341646. %Y A140271 Cf. A000005, A000203, A001221, A001222, A001248, A006530, A020639, A112798. %K A140271 nonn %O A140271 1,2 %A A140271 _Leroy Quet_, May 16 2008 %E A140271 More terms from _Stefan Steinerberger_, May 18 2008 %E A140271 a(70)-a(80) from _Ray Chandler_, Jun 25 2009 %E A140271 _Franklin T. Adams-Watters_, Jan 26 2018, added a(1) = 1 to preserve the relation a(n) | n.