21305

Appears in sequences

• Expansion of (1+x)(1+x^2)/(1-x-x^3).at n=25A003410
• Expansion of (1 - x^2)/(1 - x - x^3).at n=29A058278
• Stirling transform of A001563: a(0) = 1 and a(n) = Sum_{k=1..n} Stirling2(n,k)*k*k! for n >= 1.at n=6A069321
• a(n) = Sum_{k=0..n} C(n-k, floor(k/2)).at n=26A097333
• a(0) = 1, a(1) = 2, a(2) = 5; for n >= 3, a(n) = a(n-1) + 2*a(n-2) + a(n-3).at n=13A101399
• a(n) = a(n-3) + 2*a(n-6) + a(n-9).at n=39A109533
• Sieve performed by successive iterations of steps where step m is: keep m terms, remove the next 3 and repeat; as m = 1,2,3,.. the remaining terms form this sequence.at n=19A112561
• a(n) = index of second occurrence of A161926(n) in A114381.at n=9A161927
• Euler transform of A051064, the ruler function sequence for k=3.at n=30A173241
• Coefficient array for polynomials P(n,x)=x*P(n-1,x)+floor(n^2/4)*P(n-2,x), P(0,x)=1,P(1,x)=x.at n=59A178116
• Positions of the positive integers in the ordering of rational numbers as generated by the rules: 1 is in S, and if nonzero x is in S, then x+1 and -1/x are in S. (See Comments.)at n=24A226136
• Positions of the integers in the ordering of rational numbers as generated by the rules: 1 is in S, and if nonzero x is in S, then x+1 and -1/x are in S. (See Comments.)at n=33A226137
• Number of new rationals produced at the n-th iteration by applying the map t -> {t+1, -1/t} to nonzero terms, starting with S[0] = {1}.at n=26A226275
• Number of (17,11)-reverse multiples with n digits.at n=60A226916
• Number of nX3 binary arrays with no two ones adjacent horizontally, diagonally or antidiagonally.at n=6A228678
• T(n,k)=Number of nXk binary arrays with no two ones adjacent horizontally, diagonally or antidiagonally.at n=42A228683
• Number of 7Xn binary arrays with no two ones adjacent horizontally, diagonally or antidiagonally.at n=2A228688
• Semiprimes sp such that sp plus its digit sum is a perfect square.at n=23A244733
• Positions of 0's in A330314.at n=25A330325