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a(1) = 1; a(n) = gcd {n*(n+1), a(n-1) * (a(n-1) + 1)} for n > 1.
1

%I #12 Jun 29 2018 03:56:26

%S 1,2,6,2,6,42,14,6,6,2,6,6,14,210,30,2,6,6,2,6,42,2,6,6,2,6,42,14,30,

%T 930,62,6,6,14,210,6,2,6,6,2,6,42,86,6,6,2,6,42,14,30,6,2,6,6,14,42,6,

%U 2,6,6,2,6,42,2,6,6,2,6,42,14,6,6,2,6,6,14,42,6,2,6,6,2,6,42,86,7482

%N a(1) = 1; a(n) = gcd {n*(n+1), a(n-1) * (a(n-1) + 1)} for n > 1.

%H Harry J. Smith, <a href="/A062321/b062321.txt">Table of n, a(n) for n = 1..1000</a>

%e a(31) = gcd(31 * 32, a(30) * (a(30) + 1)) = gcd(31*32, 930*931) = 62

%t RecurrenceTable[{a[1]==1,a[n]==GCD[n(n+1),a[n-1](a[n-1]+1)]},a,{n,90}] (* _Harvey P. Dale_, Dec 21 2011 *)

%o (PARI) { for (n=1, 1000, if (n>1, a=gcd(n*(n + 1), a*(a + 1)), a=1); write("b062321.txt", n, " ", a) ) } \\ _Harry J. Smith_, Aug 04 2009

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Jul 05 2001