A227289 -id:A227289 - cp's OEIS frontend

A227288 Greatest common divisor of consecutive terms in A227113.

1, 2, 1, 3, 1, 5, 1, 7, 2, 4, 3, 3, 1, 11, 1, 13, 2, 2, 1, 17, 1, 19, 2, 4, 3, 3, 1, 23, 1, 5, 2, 4, 1, 29, 1, 31, 1, 3, 1, 5, 1, 37, 1, 3, 1, 41, 1, 43, 2, 4, 3, 5, 1, 47, 1, 7, 1, 3, 2, 4, 1, 53, 1, 5, 1, 3, 1, 59, 1, 61, 2, 2, 1, 67, 2, 2, 1, 3, 1, 71, 1

Offset: 1

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Reinhard Zumkeller, Jul 05 2013

nonn

a(n) = GCD(A227113(n),A227113(n+1));
a(2*n) > 1 by definition of A227113;
9 is the smallest odd number m with a(m) > 1: a(9) = GCD(A227113(9),A227113(10)) = GCD(14,8) = 2;
a(A227289(n)) = n and a(m) <> n for m < A227289(n).

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

a227288 n = a227288_list !! (n-1)
a227288_list = zipWith gcd (tail a227113_list) a227113_list

cp's OEIS Frontend

A227288 Greatest common divisor of consecutive terms in A227113.

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