21483

Appears in sequences

• Divisors of 2^30 - 1.at n=44A003538
• a(1) = 2; a(n+1) = a(n)-th nonprime, where nonprimes begin at 1.at n=40A025003
• a(n) = (2*n + 1)*(5*n + 1).at n=46A033571
• Bessel function Y_0(n) is a monotonically decreasing positive sequence.at n=38A046961
• Numbers k such that phi(k)/lambda(k) increases to a record value, where phi(k) is the Euler totient function (A000010) and lambda(k) is the Carmichael lambda function (A002322).at n=18A066605
• Numbers k such that (k!! + (k+1)!! - 1)/2 is prime.at n=17A076209
• 30*a(n) is the gap between sexy prime triples in the n-th sexy prime triple triple whose initial term is 17.at n=15A090891
• Heptagonal numbers for which the sum of the digits is also a heptagonal number.at n=24A117650
• Heptagonal numbers divisible by 7.at n=27A117795
• Consider the base-8 Kaprekar map n->K(n) defined in A165090. Sequence gives numbers belonging to cycles, including fixed points.at n=13A165095
• Consider the base-8 Kaprekar map n->K(n) defined in A165090. Sequence gives numbers belonging to cycles of length greater than 1.at n=10A165097
• Consider the base-8 Kaprekar map n->K(n) defined in A165090. Sequence gives least elements of each cycle, including fixed points.at n=6A165099
• Consider the base-8 Kaprekar map n->K(n) defined in A165090. Sequence gives least elements of each cycle of length > 1.at n=3A165101
• Consider the base-8 Kaprekar map x->K(x) described in A165090. Sequence gives the smallest number that belongs to a cycle of length n under repeated iteration of this map, or -1 if there is no cycle of length n.at n=3A165106
• Smallest member of cycle corresponding to n-th term of A165107.at n=5A165108
• Expansion of 1/(1-x/(1-2x/(1-3x/(1-x/(1-2x/(1-3x/(1-... (continued fraction).at n=7A168503
• Number of (w,x,y,z) with all terms in {1,...,n} and w<=2x and y>3z.at n=21A212514
• a(n) is the denominator of polygamma(2n+1, 1) / Pi^(2n+2).at n=14A255007
• Greatest common divisor of 2^n-1 and 5^n-1.at n=29A270390
• Expansion of ((Product_{n>=1} (1 - x^(3*n))/(1 - x^n)^3) - 1)/3 in powers of x.at n=17A277968