21728

Appears in sequences

• Numbers k such that (k / product of digits of k) is 1 or a prime.at n=39A001103
• Expansion of e.g.f.: sec(arctan(x)*log(x+1))=1+12/4!*x^4-60/5!*x^5+90/6!*x^6-420/7!*x^7...at n=8A012406
• Gaps of 8 in sequence A038593 (lower terms).at n=14A038655
• a(2n+1) = a(2n) + a(2n-1), a(2n) = 2*a(2n-1) + a(2n-2); a(n) = n for n = 0, 1.at n=16A048788
• a(n) = 4*a(n-1) - a(n-2), with a(0) = 0, a(1) = 2.at n=8A052530
• Row sums of array T in A053199.at n=7A053297
• a(n) = 14*a(n-1) - a(n-2); a(0) = 0, a(1) = 8.at n=4A067900
• Limit of the sequence obtained from S(0) = (1,1) and, for n > 0, S(n) = I(S(n-1)), where I consists of inserting, for i = 1, 2, 3..., the term a(i) + a(i+1) between any two terms for which 7*a(i+1) <= 11*a(i).at n=15A082630
• Row sums of triangle in A106243 (or A106242).at n=7A106327
• Expansion of (1-2x-3x^2+x^3-x^5)/(1+4x^3+x^6).at n=22A157126
• The pairs (x,y) such that (x^2 + y^2)/(x*y + 1) is a perfect square, i.e., 4.at n=15A162959
• The pairs (x,y) such that (x^2 + y^2)/(x*y + 1) is a perfect square, i.e., 4.at n=16A162959
• Numbers k with equal remainders of (product of divisors of k) mod (sum of divisors of k) and (product of proper divisors of k) mod (sum of proper divisors of k).at n=37A192035
• Number of 0..n arrays x(0..10) of 11 elements with zero 6th differences.at n=32A200447
• Number of partitions of n into distinct parts with boundary size 9.at n=35A227566
• Numbers incremented by their digit product produce a cube.at n=27A229185
• a(n) = a(n-1) + (if a(n-1) is odd a(n-2) else a(n-3)) with a(0) = 0, a(1) = 1.at n=24A254308
• Number of squares of all sizes in 3*n*(n+1)/2-ominoes in form of three-quarters of Aztec diamonds.at n=37A258440
• Maximal term of TRIP-Stern sequence of level n corresponding to permutation triple (e,23,e).at n=29A271488
• Number of distinct sets { p(i) - p(j) : 1 <= i <= j <= n } where p ranges over all permutations of [n].at n=23A343419