81313

Appears in sequences

• Number of pairs with two different elements which can be obtained by selecting unique elements from two sets with n+1 and n^2 elements respectively and n common elements.at n=43A085490
• a(n) is the genus of the modular curve associated to the principal congruence subgroup of level p(n), where p(n) is the n-th prime number.at n=29A191590
• First appearance of n in A016014, or 0 if n never occurs.at n=47A239800
• a(n) = (n + 1)*(2*n + 1)*(4*n + 9)/3.at n=30A269342
• E.g.f.: exp(x * Product_{k>0} (1 + x^k)).at n=7A293528
• Number of non-congruent solutions of x^2+y^2 == z^2+w^2 (mod n).at n=42A316148
• Let q be the n-th prime power (A246655), then a(n) = q^3 + q^2 - q; number of solutions to x*y = z*w in the finite field F_q.at n=20A367014