190050

Appears in sequences

• a(n) = number of 3-regular (trivalent) multi-graphs without loops on 2n vertices; a(n) = number of symmetric 2n X 2n matrices with {0,1,2,3}-entries with row sum equal to 3 for each row and trace 0.at n=4A108243
• Duplicate of A108243.at n=4A108247
• a(n) = C(n,6) + C(n,5) + C(n,4) + C(n,3) + C(n,2) + C(n,1).at n=24A115567
• Number of Dyck paths of semilength n such that all sixteen consecutive step patterns of length 4 occur at least once.at n=4A243820
• Array read by antidiagonals: T(n,k) is the number of k-regular loopless multigraphs on n labeled nodes, n >= 0, k >= 0.at n=74A333351
• Numbers k for which phi(A267099(k)) is equal to phi(k), but the number of 4m+1 and 4m+3 primes in the prime factorization of k (when counted with multiplicity) is not equal. Here A267099 is fully multiplicative involution swapping the positions of 4m+1 and 4m+3 primes, and phi is Euler totient function.at n=19A354194