|
%I #36 Apr 26 2015 00:14:48
%S 1,1,3,2,4,2,5,5,3,9,6,4,8,6,10,20,8,16,12,9,27,18,12,15,15,25,25,10,
%T 7,7,14,14,21,21,63,42,28,56,16,32,24,40,20,50,30,18,27,81,54,72,24,
%U 28,35,35,105,30,45,45,75,100,40,32,64,48,48,36,63,189
%N Greatest common divisors of adjacent terms in A257218.
%C a(n) = GCD(A257218(n),A257218(n+1)).
%C Each term occurs at most twice, and it is a plausible conjecture that every term will occur exactly twice.
%C A257120(n) = position of the first of not more than two occurrences of n: a(A257120(n)) = n;
%C A257475(n) = position of the second and last occurrence of n: a(A257475(n)) = n;
%C A257478(n) = distance of positions of first and second occurrence of n.
%H Reinhard Zumkeller, <a href="/A256918/b256918.txt">Table of n, a(n) for n = 1..25000</a>
%o (Haskell)
%o a256918 n = a257218_list !! (n-1)
%o a256918_list = zipWith gcd a257218_list $ tail a257218_list
%Y Cf. A257218, A257120, A257475, A257478.
%K nonn
%O 1,3
%A _Reinhard Zumkeller_, Apr 25 2015
|
