21114

Appears in sequences

• Numbers k such that 2*3^k - 1 is prime.at n=27A003307
• Numbers whose product of decimal digits equals its sum of binary digits.at n=28A064003
• a(n) is the least k such that (k*prime(n)#)^2 + 1, ((k+1)*prime(n)#)^2 + 1 and ((k+2)*prime(n)#)^2 + 1 are 3 primes, where prime(n)# is the n-th primorial.at n=19A098765
• Numbers that have exactly six prime factors counted with multiplicity (A046306) whose digit reversal is different and also has 6 prime factors (with multiplicity).at n=26A109026
• Concatenation of the numbers of equal successive digits of previous two terms read in inverse order, starting with a(1)=a(2)=1.at n=9A113721
• Alexandrian integers: numbers of the form n = p*q*r such that 1/n = 1/p - 1/q - 1/r for some integers p,q,r.at n=22A147811
• Smallest numbers containing exactly n smaller numbers when written as English number names.at n=17A159453
• Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x >= 2*y*z.at n=16A211809
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 158", based on the 5-celled von Neumann neighborhood.at n=38A270335
• Number of 4-cycles in the n-polygon diagonal intersection graph.at n=31A300552
• A(n, k) is the smallest number x > A(n, k-1) such that every letter, with repetition, that occurs in the English name of A(n, k-1) also occurs in the English name of x, with A(n, 1) = n; square array, read by antidiagonals downwards.at n=37A303380
• a(n) is the number of nonnegative integers that can be represented in a 7-segment display by using only n segments (version A010371).at n=22A331530
• a(n) = binomial(n,2)*(binomial(n-1,2) + 2).at n=17A352405
• G.f. A(x) satisfies: -x = Sum_{n=-oo..+oo} (-1)^n * x^(n*(n-1)/2) * A(x)^n.at n=10A354645
• Number of partitions of n with rank a multiple of 5.at n=45A363237
• Place n equally spaced points on each side of an equilateral triangle, and join each of these points by a chord to the 2*n new points on the other two sides: sequence gives number of edges in the resulting planar graph.at n=9A366485
• Table read by antidiagonals: Place k equally spaced points on each side of a regular n-gon and join every pair of these n*k points by a chord; T(n,k) (n >= 3, k >= 0) gives the number of edges in the resulting planar graph.at n=45A367305
• Multiplicative orders of 2+-i modulo p == 3 (mod 4) that are congruent to 2 modulo 4.at n=6A385218