20720

Appears in sequences

• a(n) = 12^n-n^2.at n=4A024142
• Numbers k such that k-th and (k+1)-st term of A038593 differ by 3.at n=18A038634
• phi(n) is equal to the sum of prime factors and exponents of n+1.at n=5A039778
• Number of n-bead necklaces with exactly four different colored beads.at n=8A056284
• Number of primitive (period n) n-bead necklaces with exactly four different colored beads.at n=8A056289
• Numbers k such that phi(k) = sigma(k+1) - sigma(k-1).at n=17A066155
• Numbers n such that sigma(n+1) = n + phi(n).at n=11A068402
• Triangle read by rows: T(n,k) is the number of n-bead necklaces with exactly k different colored beads.at n=39A087854
• The sum of a triangular array made from a negative 6 fold permutation product with shifts up and down of {2,6}.at n=42A105162
• a(n) = 16*n*(n+2).at n=35A114444
• a(n) = 64*n^2 - 16.at n=17A157913
• a(n) = 81n^2 - n.at n=15A157953
• a(n) = 324n^2 - 2n.at n=7A158305
• a(n) = 256*n^2 - 16.at n=8A158562
• Number of binary strings of length n with no substrings equal to 0001 0111 or 1010.at n=21A164483
• Expansion of e.g.f. for operads for alia algebras.at n=6A220433
• Triangular array read by rows. T(n,k) is the number of 2-colored labeled graphs on n nodes with exactly k edges; n >= 0, 0 <= k <= A002620(n).at n=32A228890
• Irregular triangular array read by rows: T(n,k) is the number of 2-colored simple labeled graphs on n nodes that have exactly k edges, 0<=k<=A002620(n), n>=1.at n=31A241669
• Number T(n,k) of primitive (= aperiodic) n-bead necklaces with colored beads of exactly k different colors; triangle T(n,k), n >= 0, 0 <= k <= n, read by rows.at n=49A254040
• Numbers k such that 8*R_k + 9*10^k + 1 is prime, where R_k = 11...11 is the repunit (A002275) of length k.at n=8A259139