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A256918
Greatest common divisors of adjacent terms in A257218.
5
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, 7, 7, 14, 14, 21, 21, 63, 42, 28, 56, 16, 32, 24, 40, 20, 50, 30, 18, 27, 81, 54, 72, 24, 28, 35, 35, 105, 30, 45, 45, 75, 100, 40, 32, 64, 48, 48, 36, 63, 189
OFFSET
1,3
COMMENTS
a(n) = GCD(A257218(n),A257218(n+1)).
Each term occurs at most twice, and it is a plausible conjecture that every term will occur exactly twice.
A257120(n) = position of the first of not more than two occurrences of n: a(A257120(n)) = n;
A257475(n) = position of the second and last occurrence of n: a(A257475(n)) = n;
A257478(n) = distance of positions of first and second occurrence of n.
LINKS
PROG
(Haskell)
a256918 n = a257218_list !! (n-1)
a256918_list = zipWith gcd a257218_list $ tail a257218_list
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 25 2015
STATUS
approved