A260641 Numbers n such that 2^n-1 is in A004782 but not in A081767.

2, 3, 7, 9, 12, 13, 17, 23, 25, 26, 31, 33, 37, 41, 44, 45, 46, 48, 49, 55, 56, 57, 61, 65, 67

Offset: 1

Author

M. F. Hasler, Nov 11 2015

Keywords

• nonn
• more

Comments

It appears that the numbers in A004782 \ A081767 are all of the form 2^n-1; this sequence gives the corresponding n-values.

Links

• M. Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems, sect. III: Binomial coefficients modulo integers, binomod.gp (v.1.4, 11/2015).

Programs

PARI

for(k=2,999, n=2^k-1; !binomod(2*n-2, n-1, n^2-n) && binomod(2*n, n,n^2-1) && print1(k", "))