1,2

Prime p divides 3^p - 2^p - 1. Quotients (3^p - 2^p - 1)/p, where p = Prime[n], are listed in A127071(n) = {2,6,42,294,15918,122010,7588770,61144062,4092816966,2366546223930,...}. Numbers n such that n divides 3^n - 2^n - 1 are listed in A127072(n) = {1,2,3,4,5,7,8,9,11,13,16,17,19,23,27,29,31,32,37,41,43,45,47,49,53,59,61,64,67,71,73,79,81,83,89,97,...}. Pseudoprimes in A127072(n) include all powers of primes {2,3,7} and some composite numbers that are listed in A127073(n) = {45,245,405,561,637,639,833,891,...}. Numbers n such that n^3 divides 3^n - 2^n - 1 are {1,4,7,...}. Primes in a(n) are {2,3,7,179,619,...}.

Do[f=(3^n-2^n-1); If[IntegerQ[f/n^2], Print[n]], {n, 1, 1000}]

Cf. A127071, A127072, A127073.

Sequence in context: A094313 A070527 A158652 this_sequence A109617 A071373 A138773

Adjacent sequences: A127071 A127072 A127073 this_sequence A127075 A127076 A127077

hard,more,nonn

Alexander Adamchuk (alex(AT)kolmogorov.com), Jan 04 2007

6 incorrect terms deleted by D. S. McNeil (d.mcneil(AT)qmul.ac.uk), Mar 16 2009 (the old version was 1,2,3,4,7,49,179,619,17807,95041,135433,393217,589825,1376257,1545601)