21891

Appears in sequences

• a(n) = a(n-1) + a(n-2) + 1, with a(0) = a(1) = 1.at n=20A001595
• Numbers k such that k-th and (k+1)-st term of A038593 differ by 3.at n=19A038634
• Integer part of the blowup factor for A025587(n).at n=13A061523
• a(n) = 2*Fibonacci(n) - (1 - (-1)^n)/2.at n=21A062114
• a(n+2) = a(n+1) + a(n) + (-1)^n, with a(1) = a(2) = 1.at n=22A066983
• a(n) = 2*Fibonacci(2*n+1) - 1.at n=10A069403
• Duplicate of A069403.at n=10A085327
• Expansion of (1 - x + 3*x^2 + 4*x^4 + 8*x^5 + 3*x^6 + x^7 + x^8) / ((1 + x)*(1 - x + x^2)*(1 - x - x^2)*(1 + x + 2*x^2 - x^3 + x^4)).at n=20A108391
• Expansion of (1 - x + 3*x^2 + 4*x^4 + 8*x^5 + 3*x^6 + x^7 + x^8) / ((1 + x)*(1 - x + x^2)*(1 - x - x^2)*(1 + x + 2*x^2 - x^3 + x^4)).at n=21A108391
• Numbers that are the sum of exactly two sets of Fibonacci numbers.at n=35A122194
• Row sums of A128586.at n=22A128587
• Numbers that have 10 terms in their Zeckendorf representation.at n=11A179250
• Shifts 4 places left under Euler transform with a(0)=0 and a(n)=1 for n < 4.at n=25A218021
• a(0)=-1, a(1)=3; a(n+2) = a(n+1) + a(n) + 2*A057078(n+1).at n=21A227104
• a(n) = a(n-1) + a(n-2) + (1 - (-1)^(a(n-1) + a(n-2))) with a(0) = 0, a(1) = 1.at n=20A253197
• Number of n X 4 0..1 arrays with no element equal to more than two of its horizontal, vertical and antidiagonal neighbors and with new values introduced in order 0 sequentially upwards.at n=8A280600
• Number of nX6 0..1 arrays with every element equal to 1, 2 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=6A300433
• Number of nX7 0..1 arrays with every element equal to 1, 2 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=5A300434
• Numbers that are the sum of seven fourth powers in exactly six ways.at n=28A345828
• Number of rational solutions to the S-unit equation x + y = 1, where S = {prime(i): 1 <= i <= n}.at n=8A362567