A046143 - OEIS

A046143

Triangle T(n, k) = gcd(2^n-1, 2^k-1), for n>=1 and 1 <= k <= n.

1, 1, 3, 1, 1, 7, 1, 3, 1, 15, 1, 1, 1, 1, 31, 1, 3, 7, 3, 1, 63, 1, 1, 1, 1, 1, 1, 127, 1, 3, 1, 15, 1, 3, 1, 255, 1, 1, 7, 1, 1, 7, 1, 1, 511, 1, 3, 1, 3, 31, 3, 1, 3, 1, 1023, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2047, 1, 3, 7, 15, 1, 63, 1, 15, 7, 3, 1, 4095, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1

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OFFSET

1,3

COMMENTS

The function T(n,k) = T(k,n) is defined for k > n but only the values for 1 <= k <= n as a triangular array are listed here.

LINKS

Table of n, a(n) for n=1..90.

Eric Weisstein's World of Mathematics,Greatest Common Divisor

FORMULA

T(n,k) = 2^gcd(n,k)-1.

EXAMPLE

Triangle begins