21188

Appears in sequences

• Numbers k such that k*2^m+1 are composites for all exponents m in the range 0<=m<=k.at n=39A061153
• Numbers k such that (2*k)!/(2*(k!)^2) - 1 is prime.at n=26A112861
• Expansion of e.g.f. exp((1-sqrt(1-4*log(1+x)))/2).at n=6A184975
• Coordination sequence for (2,4,6) tiling of hyperbolic plane.at n=28A265061
• The first Zagreb index of the Aztec diamond AZ(n) (see the Ramanes et al. reference, Theorem 2.1).at n=24A292344
• Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-2)*b(n), where a(0) = 1, a(1) = 3, b(0) = 2, b(1) = 4, b(2) = 5, and (a(n)) and (b(n)) are increasing complementary sequences.at n=14A296267
• Number of binary words w of length n such that the number of distinct blocks of length k that w contains is <= k+2 for all k.at n=32A297526
• Sequence shifts left ten places under Weigh transform with a(n) = signum(n) for n<10.at n=49A316082
• Table read by rows: T(n,k) = number of k-sided polygons in an equal-armed cross with arms of length n (see Comments in A331456 for definition) for k = 3,4,5,6,7.at n=40A333037
• Consider the figure made up of a row of n adjacent congruent rectangles, with diagonals of all possible rectangles drawn; a(n) is the number of interior vertices where exactly four lines cross.at n=46A336490
• Positive numbers whose square starts and ends with exactly 44, and no 444.at n=11A348831