21186

Appears in sequences

• a(n) = T(n,1) + T(n-1,2) + ...+ T(n-k+1,k), where k = floor((n+1)/2) and T is the array defined in A026098.at n=46A026103
• Expansion of (1-x)^(-1)/(1-x-x^2+2*x^3).at n=37A077867
• Recamán's Fibonacci variation : a(1)=a(2)=1 then a(n) = a(n-1)+a(n-2)-F(n) if that number is >0 and not already in the sequence; a(n) = a(n-1)+a(n-2)+F(n) otherwise where F(n) denotes the n-th Fibonacci number.at n=20A091484
• Structured snub dodecahedral numbers.at n=10A100151
• 11 times pentagonal numbers: 11*n*(3n-1)/2.at n=36A153449
• Sum of the squares of the first n Fibonacci numbers with index divisible by 4.at n=3A156086
• a(n) counts the distinct cubical (on alphabet of 3 symbols) billiard words with length n, acting as prefix to just k = 1 such word of length n+1 (that is, not "special").at n=14A180437
• Sum over all partitions of n of the LCM of the parts.at n=20A181844
• Lower Beatty array of sqrt(2).at n=46A182639
• Number of nondecreasing -2..2 vectors of length n whose dot product with some nonincreasing -2..2 vector equals n.at n=38A226393
• Number of 1 up, 3 down, 5 up, 7 down, ... permutations of [n].at n=12A227941
• Number of partitions of n with the property that if two summands have the same parity, then their frequencies have the same parity.at n=44A240949
• Number of (n+2)X(1+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 2 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 2 3 4 6 or 7.at n=5A252160
• Number of (n+2)X(6+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 2 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 2 3 4 6 or 7.at n=0A252165
• T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 2 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 2 3 4 6 or 7.at n=15A252167
• T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row and column sum equal to 2 3 4 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 2 3 4 6 or 7.at n=20A252167
• Number of nX6 0..1 arrays with no 1 equal to more than one of its horizontal, diagonal and antidiagonal neighbors, with the exception of exactly one element.at n=2A283570
• T(n,k) = Number of n X k 0..1 arrays with no 1 equal to more than one of its horizontal, diagonal and antidiagonal neighbors, with the exception of exactly one element.at n=30A283572
• Number of 3Xn 0..1 arrays with no 1 equal to more than one of its horizontal, diagonal and antidiagonal neighbors, with the exception of exactly one element.at n=5A283574
• Numbers that occur in range of A324580.at n=46A324541