21056

Appears in sequences

• Theta series of odd 8-dimensional 5-modular lattice O(5).at n=34A029719
• Numbers k such that 235*2^k+1 is prime.at n=29A032494
• Numbers k such that 60*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=24A056658
• Partial sums of A001157: Sum_{j=1..n} sigma_2(j).at n=36A064602
• Expansion of 2 - exp(-1 + sqrt(1-4x)).at n=6A101682
• Binomial transform of the tribonacci sequence A000073 (shifted left twice).at n=10A117189
• Least positive k such that (10^n+1)^n + k is prime.at n=41A121521
• 7 times octagonal numbers: a(n) = 7*n*(3*n-2).at n=32A153797
• a(0)=1=a(1), a(2)=2, a(3)=5; thereafter a(n+3)=4*a(n+2)-4*a(n+1)+2*a(n) for n>=1.at n=11A159035
• Numbers k such that sigma(tau(k)) equals the sum of distinct primes dividing k.at n=41A173325
• Number of 0..3 arrays x(0..n-1) of n elements with zero n-1st difference.at n=11A200149
• Number of n X 5 0..1 arrays avoiding 0 0 0 and 1 1 1 horizontally and 0 0 1 and 1 0 1 vertically.at n=14A208376
• Number of (w,x,y) with all terms in {0,...,n} and w != min(|w-x|, |x-y|, |y-w|).at n=27A213492
• Value of A114183 at end of n-th doubling run.at n=37A213656
• Triangle of Arnold L(b) for Springer numbers.at n=33A256665
• Expansion of Product_{k>=0} ((1+x^(4*k+1))/(1-x^(4*k+1)))^2.at n=32A261650
• Real part of Q^n, where Q is the quaternion 2 + j + k.at n=12A266046
• Regular triangle read by rows where T(n, k) is the number of set partitions of {1, ..., n} with no block containing k cyclically successive vertices, n >= 1, 2 <= k <= n + 1.at n=40A323955
• Expansion of e.g.f. 4 / (5 - 4*x - exp(4*x)).at n=5A355112
• Lexicographically earliest sequence of distinct terms > 0 such that the sum a(n) + a(n+1) is a substring of the concatenation (a(n), a(n+1)).at n=36A359482