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

1,1

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

Table of n, a(n) for n=1..25.

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

Prog

(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", "))

Crossrefs

Sequence in context: A103797 A262814 A328982 * A077510 A364052 A178433

Adjacent sequences: A260638 A260639 A260640 * A260642 A260643 A260644

Keyword

nonn,more

Author

M. F. Hasler, Nov 11 2015

Status

approved