21621601

Appears in sequences

• The first number that is (at least) n-fold intrinsically 3-palindromic (represented in base ten).at n=26A171702
• a(n) is the smallest integer with at least n palindromic representations of length >= 3 in bases b >= 2.at n=26A275220
• a(n) is the smallest b > 1 such that when c is equal to any of the first n composites the congruence b^(c-1) == 1 (mod c) is satisfied, i.e., smallest b larger than 1 such that any member of the set of smallest n composites is a base-b Fermat pseudoprime.at n=19A309383
• a(n) is the smallest b > 1 such that when c is equal to any of the first n composites the congruence b^(c-1) == 1 (mod c) is satisfied, i.e., smallest b larger than 1 such that any member of the set of smallest n composites is a base-b Fermat pseudoprime.at n=20A309383