cp's OEIS Frontend

A076031 Group the natural numbers so that the n-th group contains the smallest still-available set of n numbers whose product is a square.

%I A076031 #20 Mar 15 2025 11:30:20
%S A076031 1,2,8,3,4,12,5,6,7,210,9,10,11,13,1430,14,15,16,17,18,1785,19,20,21,
%T A076031 22,23,24,168245,25,26,27,28,29,30,31,409045,32,33,34,35,36,37,38,39,
%U A076031 119629510,40,41,42,43,44,45,46,47,48,293493662,49,50,51,52
%N A076031 Group the natural numbers so that the n-th group contains the smallest still-available set of n numbers whose product is a square.
%C A076031 The first n-1 numbers of row n are selected by simply choosing the smallest n-1 numbers which have not yet been used. The remaining number is then chosen to be the smallest possible unused number such that the product of the n numbers is a square. - _Sean A. Irvine_, Mar 14 2025
%H A076031 Sean A. Irvine, <a href="/A076031/b076031.txt">Table of n, a(n) for n = 1..1540</a> (rows 1..20 flattened)
%H A076031 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a076/A076031.java">Java program</a> (github)
%e A076031 1;
%e A076031 2, 8;
%e A076031 3, 4, 12;
%e A076031 5, 6, 7, 210;
%e A076031 9, 10, 11, 13, 1430;
%e A076031 14, 15, 16, 17, 18, 1785;
%e A076031 ...
%Y A076031 Cf. A076027, A076028, A076029, A076030.
%Y A076031 Cf. A076596, A076696.
%K A076031 nonn,tabl
%O A076031 1,2
%A A076031 _Amarnath Murthy_, Oct 01 2002
%E A076031 Corrected and extended by _Hans Havermann_, Nov 09 2002