21376

Appears in sequences

• Expansion of e.g.f. sinh(tan(x)*tan(x)) (even powers only).at n=4A009613
• arcsin(tan(x)*tan(x))=2/2!*x^2+16/4!*x^4+392/6!*x^6+21376/8!*x^8...at n=4A012388
• Duplicate of A009613.at n=3A012390
• Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 73.at n=27A031571
• Fibonacci iteration starting with (1, a(n)) leads to a "nine digits anagram".at n=35A034587
• Numerators of continued fraction convergents to sqrt(553).at n=6A042058
• a(n) = denominator of the continued fraction which has the positive integers which are <= n and are coprime to n as its terms. The terms are written in order from 1 for the integer part, to n-1 for the final term of the continued fraction.at n=13A127615
• prime(n)*( prime(n)-n ).at n=38A161522
• Triangle T(n,k), 0<=k<=n, read by rows given by [1,1,2,1,2,1,2,1,2,1,2,...] DELTA [1,1,0,0,0,0,0,0,0,...] where DELTA is the operator defined in A084938.at n=41A167656
• Number of triangular n X n X n arrays colored with integers 0 upwards introduced in row major order, with no element equal to any neighbor, and containing the value n(n+1)/2-2.at n=19A211899
• Nonprime numbers k that divide the sum of remainders of k' mod m, for m from 1 to k', where k' is the arithmetic derivative of k.at n=7A248135
• Partial sums of A256970.at n=39A256971
• Decimal representation of the x-axis, from the origin to the right edge, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 267", based on the 5-celled von Neumann neighborhood.at n=14A280462
• Primitive practical numbers of the form 2^i * prime(k).at n=37A308710
• Number of integer partitions of n with at least one pair of consecutive divisible parts.at n=37A328221
• a(n) is the number of decompositions of H(n,1) into disjoint unions of H(j,k) where H(j,k) is the set of numbers { (2*i-1)*(2*k-1), 1 <= i <= j }.at n=35A336739
• a(n) is the smallest abundant number of the form 2^e * prime(n).at n=37A341361
• With p = prime(n), a(n) is the least composite k such that A001414(k) = p and k+p is prime, or 0 if there is no such k.at n=41A346501
• a(n) = A376877(n) / p where p is the largest prime factor of A376877(n).at n=40A376874
• Numbers which can be written in precisely one way as sum of a subset of their proper divisors and that have exactly one subset of their divisors such that the complement has the same sum.at n=52A378530