18470

Appears in sequences

• "BFK" (reversible, size, unlabeled) transform of 2,2,2,2...at n=20A032043
• a(n) = smallest number m > 0 such that n followed by m 1's yields a prime, or -1 if no such m exists.at n=55A069568
• Smallest number m >= 0 such that n followed by m ones yields a prime; a(p) = -1 if no such m exists.at n=55A083747
• Number of (w,x,y,z) with all terms in {1,...,n} and 2|w-x|=|x-y|+|y-z|.at n=30A212575
• Expansion of Sum_{k>=1} phi(k) * x^k/(1 - x^k)^4, where phi = Euler totient function (A000010).at n=46A309323
• a(n) = (n^3 + 6*n^2 + 17*n + 6)/6.at n=46A341209
• a(n) is the number of free polyiamonds of n cells with chessboard coloring.at n=12A359689