18630

Appears in sequences

• a(1)=4; a(n) is the smallest number m > a(n-1) such that Omega(m + a(i)) = Omega(m) - Omega(a(i)) for i = 1..(n-1) where Omega(k) is the number of prime divisors of k counted with multiplicity.at n=3A059391
• a(n) = 18*(n - 2)*(2*n - 5).at n=23A060787
• a(n) = prime(n)^2 - prime(n+1).at n=32A062235
• Numbers n such that sigma(n)/phi(n) is prime.at n=31A067780
• Number of general plane trees whose n-th subtree from the left is equal to the n-th subtree from the right, for all its subtrees (i.e., are palindromic in the shallow sense).at n=11A073192
• Diagonal in array of n-gonal numbers A081422.at n=26A081435
• Indices m such that A128646(m)-1 is prime, where A128646 = denominator of partial sums of 1/(p(i)-1).at n=54A137689
• Convolution of A000108 (Catalan numbers) with A126120 (Catalan numbers interpolated with 0's).at n=10A161006
• Multiples of 23 whose digit reversal - 1 is also a multiple of 23.at n=34A166400
• Numbers n such that sigma(n) = 11*phi(n) (where sigma=A000203, phi=A000010).at n=2A171257
• a(n) = (7*n+2)*(7*n+5) = 49*n^2 + 49*n + 10.at n=19A177060
• Numbers k such that sopfr(k + omega(k)) = sopfr(k), where sopfr(i) = A001414(i) and omega(i) = A001221(i).at n=20A187878
• Irregular array T(n,k) of the numbers of non-extendable (complete) non-self-adjacent simple paths incorporating each of a minimal subset of nodes within a square lattice bounded by rectangles with nodal dimensions n and 4, n >= 2.at n=30A214510
• Irregular array T(n,k) of the numbers of non-extendable (complete) non-self-adjacent simple paths incorporating each of a minimal subset of nodes within a square lattice bounded by rectangles with nodal dimensions n and 8, n >= 2.at n=12A214605
• Triangle read by rows: T(n, k) = t(n-k, k), where t(0,0) = 1, t(n,m) = 0 if n < 0 or m < 0, else t(n,m) = f(m)*t(n-1,m) + f(n)*t(n,m-1), and f(n) = 6*n + 3.at n=12A257625
• Number of (n+1) X (5+1) 0..1 arrays with every 2 X 2 subblock ne-sw antidiagonal difference nondecreasing horizontally and nw+se diagonal sum nondecreasing vertically.at n=7A258551
• Expansion of Product_{n>=1} (1 - x^(5*n))/(1 - x^n)^4 in powers of x.at n=11A278680
• Numbers k such that 4*10^k - 71 is prime.at n=17A294917
• a(n) = 3*2*1 - 6*5*4 + 9*8*7 - 12*11*10 + 15*14*13 - 18*17*16 + ... - (up to the n-th term).at n=33A319886
• Number of compositions of n such that the set s of parts and multiplicities satisfies s = {1..max(s)}.at n=17A335942