21708

Appears in sequences

• a(n) = a(n-1) + a(n-1-(number of odd terms so far)).at n=38A007604
• Same rule as Aitken triangle (A011971) except a(0,0)=0, a(1,0)=1.at n=48A046936
• Numbers k such that prime(k) + prime(k+1) + prime(k+2) is a square.at n=25A076305
• a(n) = A077708(n+1)/A077708(n).at n=18A077709
• Numbers that have exactly seven prime factors counted with multiplicity (A046308) whose digit reversal is different and also has 7 prime factors (with multiplicity).at n=2A109027
• Nonnegative values x of solutions (x, y) to the Diophantine equation x^2+(x+47)^2 = y^2.at n=11A118675
• a(n) = n*(2*n^2 + 5*n + 15)/2.at n=27A163673
• Numbers k such that sigma(tau(k)) equals the sum of distinct primes dividing k.at n=42A173325
• Number of n X 5 binary arrays with each 1 adjacent to exactly two 0's.at n=5A183333
• Number of n X 6 binary arrays with each 1 adjacent to exactly two 0's.at n=4A183334
• T(n,k) = Number of n X k binary arrays with each 1 adjacent to exactly two 0's.at n=49A183335
• T(n,k) = Number of n X k binary arrays with each 1 adjacent to exactly two 0's.at n=50A183335
• Numbers n such that n^2 is divisible by the sum of the distinct prime divisors of n^2 + 1.at n=12A196219
• Smallest number m (not ending in a 0) such that m and its digit reversal A004086(m) both have n prime factors (counted with multiplicity).at n=6A237912
• Smallest number m > 1 (not ending in a 0) such that m and the digit reversal of m have n prime factors (counted with multiplicity). Palindromes are included.at n=6A237913
• Expansion of e.g.f. exp( x * (exp(3 * x) - 1) ).at n=6A351737
• Composite k such that the primorial inflation of k is a sum of distinct primorial numbers.at n=21A351959
• Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = n! * Sum_{j=0..floor(n/2)} k^(n-j) * Stirling2(n-j,j)/(n-j)!.at n=51A362839
• Expansion of 1/(1 - 2*x - 7*x^2)^(3/2).at n=7A374487
• Number of cells that are a distance of n away in an order-5 hyperbolic square tiling.at n=11A377322