56020

Appears in sequences

• Triangle read by rows: semigroups of order n with k idempotents, considered to be equivalent when they are isomorphic or anti-isomorphic (by reversal of the operator).at n=25A058123
• Sums of squares of primitive roots of primes.at n=20A089453
• Number of binary sequences of length n with no subsequence 0101.at n=17A118870
• Expansion of 4*x^2/(1 - x - 9*x^2 + x^3).at n=10A271945
• Numbers n such that 17^n is the highest power of 17 dividing A240751(n).at n=4A286008