18042

Appears in sequences

• Numbers having four 6's in base 9.at n=2A043480
• Number of rooted trees with n nodes with every leaf at height 9.at n=19A048814
• Number of permutations of 1..n containing the relative rank sequence { 132465 } at any spacing.at n=3A159089
• Number of permutations of 1..n containing the relative rank sequence { 143265 } at any spacing.at n=3A159109
• Number of permutations of 1..n containing the relative rank sequence { 154326 } at any spacing.at n=3A159127
• Number of permutations of 1..n containing the relative rank sequence { 214365 } at any spacing.at n=3A159141
• Sequence of the "Natural Jewels": a natural jewel is a number that is totally enclosed by prime numbers in a version of Ulam Spiral.at n=14A172294
• Number of, not necessarily connected, regular simple graphs on n vertices with girth at least 4.at n=16A185314
• Smallest sets of 7 consecutive abundant numbers in arithmetic progression. The initial abundant number is listed.at n=7A228964
• Number of partitions p of n that do not include (min(p) + max(p))/2 as a part.at n=36A238481
• Numbers n such that sigma(n) - n = Sum_{k|n, k < n} sigma*(k), where sigma(n) is the sum of the divisors of n and sigma*(k) is the sum of the anti-divisors of k.at n=11A259536
• Squarefree numbers n such that n^2 + 1 and n^2 - 1 are semiprime.at n=25A268697
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 105", based on the 5-celled von Neumann neighborhood.at n=29A270162
• Number of permutations in S_{2*n+3} containing the pattern 2143...(2n)(2n-1).at n=3A271648
• a(1) = 102735, a(n) = prime(n-1)*a(n-1) but products that are not in A010784 are first reduced as in A320486 (see comments); continue until zero is reached.at n=25A321149
• Averages k of twin primes such that the sum (with multiplicity) of prime factors of k-1, k and k+1 is prime.at n=38A340060
• Numbers on the square spiral board that are enclosed by four primes.at n=15A341542
• Twin primes x, represented by their average, such that x is the first and x+18 the last of three successive twins.at n=5A350541
• Triangle read by rows: T(n, k) (2 <= k <= n) is the smallest positive integer m >= k such that the digits of m expressed in base n are the same as the first digits in base k.at n=18A380293
• Triangle read by rows q(b1,b2) with 1<b1<b2 with q(b1,b2) being the least integer k equal to or greater than b1 such that all the digits of k read in base b2 are the beginning digits of k read in base b1; or 0 iff b2 is perfect power, m^k (A001597), and b1 is m^j, 0<j<k.at n=13A380564