21204

Appears in sequences

• Coefficients of high-temperature series for specific heat of spin-1/2 Ising model on a cristobalite lattice.at n=7A005392
• Sum{T(n-k,k)}, 0<=k<=[ n/2 ], T given by A026670.at n=20A026680
• Number of labeled servers of dimension 8.at n=4A027395
• Smallest composite which when sum of prime factors is repeatedly subtracted reaches a prime after n iterations.at n=29A053093
• A 3-way generalization of series-parallel networks with n unlabeled edges.at n=11A058534
• Numbers k such that the three second-degree cyclotomic polynomials x^2 + 1, x^2 - x + 1 and x^2 + x + 1 are simultaneously prime when evaluated at x=k.at n=16A087277
• Triangle T, read by rows, where column n of T = column 0 of T^(2^n) for n>0, such that column 0 (A129092) equals the row sums of the prior row, starting with T(0,0)=1.at n=30A129100
• Column 2 of triangle A129100; also equals column 0 of matrix power A129100^4.at n=5A129102
• Triangle T, read by rows, where row n (shifted left) of T equals row 0 of matrix power T^n for n>=0.at n=38A129104
• Nonascending wiggly sums: number of sums adding to n in which terms alternately do not increase and do not decrease.at n=19A129853
• Values of n such that (sigma(sigma(n))-phi(phi(n)))/n is an integer (the corresponding integral ratios are given in A136132).at n=24A136131
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 1, 1), (1, -1, 1), (1, 1, -1), (1, 1, 0)}.at n=8A149423
• 3 times 12-gonal (or dodecagonal) numbers: a(n) = 3*n*(5*n-4).at n=38A153448
• Numbers n such that n+(n+1), n^2+(n+1)^2, n+(n+1)^2, n^2+(n+1) are all prime.at n=28A216270
• Number of partitions of n such that (maximal multiplicity of parts) > (multiplicity of the least part).at n=43A240304
• Number of (5+1)X(n+1) 0..1 arrays with every 2X2 subblock ne-sw antidiagonal difference unequal to its neighbors horizontally and nw+se diagonal sum unequal to its neighbors vertically.at n=12A253702
• Triangle read by rows: T(n,k) is the number of subpermutations of an n-set whose orbits are each of size at most k, and without fixed points. Equivalently, T(n,k) is the number of partial derangements of an n-set each of whose orbits is of size at most k.at n=31A261762
• Decimal representation of the x-axis, from the left edge to the origin, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 777", based on the 5-celled von Neumann neighborhood.at n=19A283916
• Main diagonal of array in A358298.at n=23A358301
• Expansion of (1/x) * Series_Reversion( x / ((1+x) * B(x)) ), where B(x) is the g.f. of A001764.at n=6A381905